Reducing Inequalities by Investing in Early Childhood Education and Care

Research on child development has seen impressive progress in recent decades, partly driven by advances in neuroscience. Knowledge of the stages of children’s development has improved with an increasing awareness of the importance of the very first years and of pre-natal conditions, but also of the continuous brain development throughout later stages of childhood and beyond. Building on these findings and those from other disciplines, evidence has accumulated on the role of the family environment (e.g. income, living conditions, parenting practices) as well as the influence of other environmental aspects (e.g. communities, neighbourhoods, available services) on children’s learning, development and well-being. Differences in the family environment translate, on average, into differences in opportunities from an early age. These mechanisms are often exacerbated by differences in the broader environment. Research has led to a better understanding of the multiple factors that contribute to the opportunity gaps that children experience in the early years, how they build up, and how they might accrue or accumulate later in life.

The deeply entrenched mechanisms that lead to the reproduction of social inequalities act in a context of high, and sometimes rising, economic inequality in most OECD countries, with the richest families capturing a large share of the national income and wealth. At the other end of the distribution, poverty rates have remained at high levels in many OECD countries. A range of economic and social policies shape economic and social inequalities, with those around children and families playing an important role in the early years of life, as discussed in the following chapters of this report.

This chapter addresses the following questions:

• What are the main research advancements in the understanding of how young children develop?

• What are the main drivers of the build up of opportunity gaps in the early years of children’s development?

This chapter starts by reviewing some of the main findings from recent research on how children develop and learn in the early years, and the factors that support or hinder children’s development and learning. It then presents a framework of the dimensions of vulnerability for young children that is used throughout this report, as well as evidence of inequalities in achievement at an early age between vulnerable children and other children. Finally, the chapter discusses the processes that lead to the build up of inequalities, putting aside the role of policies that is discussed in depth in Chapters 4 to 10.

This section provides a brief overview of some of the key findings from recent research from multiple disciplines on how children develop.

Advances in neuroscience and contributions from other disciplines (e.g. paediatrics) have led to a better understanding of how the brain develops and how children learn (see Annex A, Workshop 1). Neuroscience research has demonstrated that children have a wide range of early skills (Bendini, 2022[1]). From infancy, children have an intuitive concept of numbers and gain knowledge of objects, which guides their understanding of the physical world. Children also gain an early understanding of people’s actions and goals, which serves the development of their own motor skills and their understanding of people’s intentions and mental states. Children have an early sensitivity to social relationships, communication and language, which helps them learn about and from other people.

Children’s early development and learning involve all areas of cognition and are underpinned by a structurally and functionally complex neural architecture. Children’s learning in all areas of core knowledge depends on general skills and processes such as executive function (focusing attention, memory), imagination, metacognition (learning to learn) and motivation. The foundations of these skills are already present at birth, with clear evidence that infants can recognise stimuli experienced prenatally.

A key contribution of recent research has been to describe the phases of development during early childhood in particular, and later stages more generally. New research using neuroimaging has enabled the development of reference standards for normal brain development and ageing through a series of brain charts spanning from a 15-week-old foetus to a 100-year-old adult (Bethlehem R.A.I., 2022[2]). The pre-natal period and the first three years of life appear as a critically sensitive period for various forms of development and learning. Brain development starts during the very first days of pregnancy through to the last trimester of pregnancy, in which the brain is considered as fully developed. From the end of the pre-natal period, children learn the characteristics of their environment and culture through these structured brain networks (Ministère des Solidarités et de la Santé, 2020[3]).

This research also explains the phases of development at a more granular level. Babies’ brain networks are very similar to those of adults, which enable rapid development of phonology, vocabulary and syntax during the first three years of life. Babies’ brains act like sponges, soaking up all kinds of environmental information, particularly from their parents or caregivers. In the first year, for example, babies can learn any language, but that capacity is quickly narrowed based on the sounds or signs they hear or see. Starting at about 18 months to two years of age, brain development involves both strengthening important connections and decreasing ones that are not being used. This period continues throughout childhood. Aspects of brain development involved in processes like perception, language and consciousness peak at about age two, meaning that the brain becomes increasingly specialised to focus on relevant inputs and produce relevant outputs (e.g. the sounds specific to the language(s) the child is learning) after this time. Learning – which concerns all aspects of cognition, including language but also the physical properties of objects, numeracy, geometry, navigation in space, as well as reflexive cognition such as having a consciousness of the world, knowledge of oneself and others – proceeds in a similar way across all of these domains. Children progressively learn to process emotions, interact in social settings and develop more complex communication skills, in ways that are adaptive to their contexts and cultures.

Because of enormous capacity for learning in the early years, children’s development is also particularly fragile at this point. Serious nutritional and health deficits have the potential to have long-term negative effects when they occur in the early years, as discussed later in this chapter (see Annex A, Workshop 1).

Children develop through play from the first weeks of life. Free play, initiated by children, is at the heart of their development and allows them to build an increasing understanding of the world and their environment (see Annex A, Workshop 1). Through play, children can learn concepts relating to literacy, numeracy and science. Play stimulates curiosity, communication and active emotional engagement. Learning and play are fully compatible: playful learning captivates children's minds in ways that support better academic and social outcomes (Hirsh-Pasek et al., 2008[4]). For these reasons, scientific evidence suggests that reducing the role of play in children’s lives and focusing more on the development of academic skills from an early age is not a good direction. Play also helps children develop their motor skills while offering many opportunities for parents to fully engage with their children. Overall, play helps children’s development in multiple areas while fostering their well-being. It is in this vein that play is recognised as a right of the child according to Article 31 of the United Nations Convention on the Rights of the Child.

Several paediatric scientific societies have sounded the alarm on the decline in children's play time (Ginsburg, 2007[5]). This trend has been observed in the United States but has also been documented in some other countries including Canada and the United Kingdom (Loebach et al., 2021[6]), although there is no international data on the time that children spend at play. The trend is partly driven by a decline in outdoor play, but is also observed for play at home and in early childhood education and care (ECEC) settings (Colliver et al., 2022[7]). The feeling that children cannot play safely outside of the home unless they are under close adult supervision, especially in certain neighbourhoods or communities, is an important factor behind this decline in some countries. In addition, the tendency for parents to focus more on activities that aim specifically at developing children’s academic skills leaves less time for play, especially unstructured play. Other factors include the increase in the percentages of families with two working parents and families with a single parent. In ECEC settings in countries such as the United States, the last year(s) of pre-primary education have generally become more similar to the first year of primary education, with a strong focus on reading and the development of other academic skills, to the detriment of time for play (Schlesinger et al., 2020[8]).

The World Health Organisation has highlighted the risk that screen time replaces time for non-digital play and has provided guidelines on time spent in physical activity for young children (World Health Organization, 2019[9]). These guidelines recognise that physical activity mainly takes place in various forms of play during which children are active, such as playing with objects, but also pretend play.

Research from various disciplines has discussed the core role that the home environment, parents and caregivers play in the quality of the interactions that children experience with others, which is a key driver of their development, learning and well-being.

The neurosciences and psychology fields have shown that the development of the brain and learning in the early years of life are particularly sensitive to cognitive stimulation and therefore to the interactions that children have with parents, caregivers and other adults. The foundations of brain architecture are established early in life through a continuous series of dynamic interactions between genetic influences and environmental conditions and experiences (Fox, Levitt and Nelson III, 2010[10]). Children have a social appetite from birth, with a preference for social stimuli: human faces and bodies, biological movements, voices, behaviours addressed to them, etc. They pay attention when adults talk to them and vocalise more often when adults talk around them.

Young children therefore quickly become actors in the social world, particularly motivated to participate. They are active agents of their learning, rather than passive subjects (see Annex A, Workshop 1). They have internal models of the environment that surrounds them and are able to analyse its regularities. Infants update and modify these models thanks to error and surprise signals when their initial expectations prove false. This means that curiosity and experimentation are crucial for early learning and should be encouraged, and that errors should be seen as a natural part of this process. At the same time, children need adult guidance to focus their attention on relevant objects and dimensions, as well as to develop language, which is a crucial vector for the acquisition of further knowledge. Frequent and rich verbal interactions with adults are thus critical for children in their early years. The quantity and quality of speech addressed to children (variety of words and structures, rich and interconnected sentences, encouragement, songs and rhymes) has impact on the development of children’s language skills. Parental engagement in learning activities, such as speaking and reading to children from an early age, is critical, as is parental awareness of their children’s abilities, such as their curiosity.

Parent-baby interaction is a source of pleasure for both the adult and the baby, and initiates the virtuous circle of communication. The infant becomes attached to people who respond quickly, warmly and in the most appropriate way possible to his behaviour; and their feeling of security promotes learning. Beyond parents’ capacity to positively support children’s development through rich interactions, there is evidence that children raised in stable and secure environments tend to exhibit a future-oriented mindset and develop strategies that entail anticipation and planning for future events, which are personal traits and skills that are associated with positive life outcomes, such as enhanced academic achievement and improved overall health and well-being (Delgado et al., 2024[11]).

Children benefit from having quality interactions with both parents. For instance, some studies have looked at the specific role of fathers on child development in families with opposite-sex parents. A study in the United Kingdom – using data from the Millennium Cohort Survey linked to educational records – found that greater paternal involvement in structured educational activities (like reading and playing) provides an educational advantage to children in the first year of primary school (Norman, 2023[12]). The earlier a father gets involved in the child’s life, the more likely he is to be involved later when the child is older, which has benefits for a child’s educational progression.

Building on findings from the field of neurosciences, but from a different perspective, research in the social sciences has attempted to identify the various factors that make up the quality of the home environment and explain its crucial influence on children’s development. Similar to ECEC settings (OECD, 2021[13]) (see Chapters 6 and 7), the quality of the home environment can be characterised by structural and process factors (Duncan et al., 2023[14]). Structural conditions include absolute level of income, number of books and toys in the home, amount of quality food for children, regularity and sufficiency of sleep, and safety of the home environment, including exposure to second-hand smoke and other toxins. Process measures include both quantity and quality of the behaviours reflecting parenting practices or the interactions children have with others within the home environment. For instance, the quality of the home environment is measured through the Home Observation for Measurement of the Environment (HOME) instrument that includes information on the family composition, gender roles, the division of childcare in families, the acceptability and advisability of different forms of discipline, and the digital environment in which children live, although this measure is not relevant to all cultural groups (Lansford et al., 2023[15]).

More generally, research in the social sciences (e.g. sociology, economics) has demonstrated the critical role of family status on a large set of life outcomes, with various drivers of inequality already at play in early childhood (see Annex A, Workshop 1). These results are discussed later in this chapter.

A large number of studies from multiple disciplines have highlighted that stress (i.e. the state of mental or emotional tension) stemming from trauma, neglect or other difficult situations in the early years can have profound effects on children’s development and throughout their life. Recent research has aimed to quantify the negative effect of stress and trauma on children’s development and to better understand the mechanisms behind these effects.

During early childhood, the brain is particularly sensitive to stress. Chronic exposure to stress in early developmental stages can disrupt cognitive and emotional aspects of normal development, causing a significant delay in the ability to learn. Elevated maternal stress during pregnancy is associated with atypical brain development and higher risk for psychopathology in offspring (Nolvi et al., 2023[16]). High levels of stress can diminish the normal functioning of essential nervous systems that are located in the prefrontal cortex, which are responsible for moderating social behaviour, planning and emotions (Shay, Shavit and Sasson, 2023[17]). Childhood adversity may accelerate a shift from exploration to exploitation decision-making behaviour (i.e. falling back on a familiar method versus trying a new, exploratory method), with wide-ranging effects on the adult brain and mind (Frankenhuis and Gopnik, 2023[18]).

Supportive environments during early postnatal life may promote brain development and reverse atypical developmental trajectories induced by pre-natal stress. A study found effects on brain activity of psychosocial deprivation around 2 years of age among institutionalised children in orphanages in Romania (Vanderwert et al., 2010[19]). However, removing children from psychosocial deprivation before the age of two had profound effects on brain activity. Similar experiences at 42 months of age found no effects of the intervention on the brain activity; this suggests that the intervention had its greatest effect when enacted before 24 months of age. By 8 years of age, with the continued experience of an enriched environment, and the absence of psychosocial deprivation, these children showed patterns of brain activity similar to those of children who had not suffered from deprivation. The timing effects in the findings suggest a sensitive period after which brain activity in the face of severe psychosocial deprivation is less amenable to recovery.

Children’s health is closely related to their learning and development. This relationship has been known for decades, and has driven policies supporting good nutrition and regular health and development reviews. This section focusses on some recent developments.

Recent research has looked at how pre-natal conditions influence children’s health and early stages of development with possible long-term implications. For instance, a recent collection of articles in medical sciences have highlighted the multitude of maternal factors that influence pregnancy, childbirth, and the health of both the mother and child during pregnancy and long after birth (Tong et al., 2024[20]). These factors include mothers’ pre-existing medical conditions (e.g. diabetes), nutrition, maternal stress and mental health, environmental exposures (e.g. smoking, alcohol and pollution), genetics, and obesity. Heightened maternal stress has been related to preterm birth, which is a major cause of death in young children and of lifelong disability (Sutton and Darmstadt, 2013[21]).These findings point to the need for policies that support families during pregnancy and mitigate maternal stress as a preventive measure, in addition to those targeted at families and children in the early years after birth.

Sleep has also been identified as a key factor for children’s development. Sleep ensures good health and physical development, as well as optimal emotional and cognitive development (Chaput et al., 2017[22]). It is one of the key elements of learning, thanks in particular to rapid reactivations (replay) of events preceding sleep episodes. These reactivations allow for consolidation in long-term memory but also the discovery of abstract relationships between events. For example, learning of vocabulary is facilitated by naps taking place after exposure to new words. Likewise, in kindergarten, learning in the morning is reinforced by a nap at the beginning of the afternoon (Kurdziel, Duclos and Spencer, 2013[23]).

Studies over the last decades have looked at the effect of exposure to pollution on children’s health and development. Exposure to indoor air pollution (from cooking fuels and passive smoke during pregnancy) are associated with delays in children’s development (Herrmann, King and Weitzman, 2008[24]) (Grippo et al., 2023[25]). Outdoor air pollution coming from suspended particulate matter (PM) (especially PM2.5 but also PM10) is considered as the most dangerous to human health. When such exposure occurs during pre-natal development, this can lead to lower birth weight of a baby and breathing problems. During childhood, exposure can lead to airway inflammation, coughing, nose and throat irritation, acute respiratory infection (including bronchitis and pneumonia) and chronic respiratory infection (including asthma) (UNICEF, 2023[26]).

In home environments, young children interact with digital technologies (tablets, mobile phones, computers, etc.) at increasingly younger ages, for a wide range of activities. Digitalisation broadens the bundle of skills needed to thrive in a technology-rich world. Early childhood can be a window of opportunity for introducing children and families to safe, creative and educational uses of digital technology, as it is a time when young children gradually gain autonomy in using digital tools, but remain more accepting of adult guidance and supervision (OECD, 2023[27]).

However, research has also paid increasing attention to the negative effects of passive exposure to screens and digital technologies on children’s development. For instance, passive use of screens at important times (waking up, going to bed, during meals) has been shown to replace rich interactions with adults and playtime, with detrimental effect on children’s sleep and development. For example, background television interrupts children in their play and can prevent them from learning to concentrate. Regular use of the screen as a means of calming children could hinder them in developing their own emotional regulation. Furthermore, digital content that claims to have educational properties has often not been evaluated. It is therefore important that children are protected from harmful effects and equipped with knowledge to thrive in digitally enhanced societies (OECD, 2023[27]). Research points to several principles for using digital technologies with young children, such as ensuring that children are actively engaged and work together, and that activities with digital technologies are limited in time and do not replace or limit other play and learning opportunities.

In addition, screens might distract both parents and children and affect the quality of the interactions between them. Neuroscientists insist on the risks of disruptions caused by technology on human interactions (and particularly those between parents and children), so-called “technoference”. A review of 27 studies of parental mobile device use during parent-child interactions found that device use may compromise the development of a secure attachment relationship and children’s general development (Kildare and Middlemiss, 2017[28]). A study of interactions during meals between mothers and their children (around 6 years old) found that mobile use by mothers was associated with 20% fewer verbal and 39% fewer non-verbal interactions, as well as 28% fewer encouragements, compared with no mobile use (Radesky et al., 2015[29]).

Inequalities in children’s development, learning and well-being, depending on their socio-economic background and other characteristics, come into play before birth and continue into the very early years of life. These inequalities are shaped by household income inequalities. Evidence on early inequalities and how they tend to reproduce is needed to inform policy design, implementation and assessment. In particular, this can help identify groups of children who might be in more vulnerable situations, called “vulnerable children” throughout this report, and require specific policy attention.

Children come from diverse socio-economic, linguistic and cultural backgrounds. These different characteristics can, in themselves, represent advantages or disadvantages for children. They may be seen as an asset that can lead to greater resilience, more knowledge of and openness to other cultures. However, children from socio-economically disadvantaged or minority backgrounds are generally more vulnerable, as they are at risk of having weaker outcomes in education and in life more generally. Research has identified a range of consistent predictors that put children at higher risks of poor development and learning conditions, starting in the early years. Those predictors can help design policies that aim to mitigate inequalities. Risk factors include parents’ socio-economic status (SES), immigrant background and parents speaking a minority language at home, being from minority racial or ethnic groups, and having special education needs (SEN). These risks factors are often interrelated. This report looks at inequalities among children along these various dimensions, while recognising that children can be exposed to multiple sources of vulnerabilities (Figure 3.1).

A child’s socio-economic background is determined by their parents’ SES, which includes several dimensions that contribute to the likelihood of experiencing a variety of stressors (see sections below) and are therefore critical for young children’s outcomes:

• Income: Low income can lead to poor housing and living conditions, difficulty buying the things children need, and less access to health services. Poverty translates into stress, psychological vulnerability, and weaker ability to adopt practices that support children’s development.

• Parents’ educational attainment: Research has shown that parents’ education, and particularly maternal education, is related to the type and amount of practices with children (Ma, 2022[30]). For instance, higher-educated mothers are more likely to engage in daily reading, rich verbal interactions and pleasant interactions with children.

• Occupational prestige: The type of occupation, beyond the income it provides, contributes to parents’ status, ability to engage with peers and the overall family social capital. Work type also influences values and beliefs about children’s development, although differences in values and beliefs between white- and blue-collar occupations have reduced over time.

• Employment status: Precarious employment situations in the family such as short-term contracts, informal employment, or a single working member in the family create risk to income and can generate stress at the family level, with impacts on children.

• Household characteristics: The risk for one-parent households to be exposed to poverty and social and emotional difficulties are higher, and parents’ mental health has strong impacts on children’s development. Single parents might have less time to engage in rich interactions with their children. They might also be more isolated than dual-parent families, and less well connected to the larger community, which can impact children as social capital is associated with children’s outcomes.

Young children with an immigrant background are vulnerable partly because of the vulnerability of their parents. Migration means a change in the individual’s physical and social environment from the one that they were originally familiar with (Cerna et al., 2021[31]). The degree of adversity differs greatly across individuals, depending on their migration experience and personal circumstances. It can range from the small challenge related to understanding how services to children and families are organised to disruption in family bonds and social networks. Children with an immigrant background often experience a different language at home than the one used in the education system.

Children from ethnic minority groups and Indigenous communities are different groups; hence, they need varying policy responses based on their specific needs (Cerna et al., 2021[31]). Nonetheless, they often face significant and similar challenges when it comes to education, such as lower educational attainment and higher dropout rates. The reasons are complex but relate to factors that start in the very early years such as discrimination, bullying, language barriers and misunderstood cultural variations.

Children with special education needs (SEN) is a term used in many education systems to characterise the broad array of needs of children affected by learning disabilities, physical impairments and/or who suffer from mental disorders (Cerna et al., 2021[31]). The challenges for parents, ECEC settings and schools in providing high-quality education to children with SEN relate to the identification of their needs and the organisation and adequate resourcing of responses. This type of vulnerability is different in nature from dimensions stemming from family characteristics, but shares similarities in the sense that systems need to adapt to respond to these needs.

Some of these risks overlap or accumulate, and are generally framed around the concept of intersectionality, or the way in which inequality is associated with multiple social categories of identity and compound inequities in outcomes for individuals. Intersectionality at the family level translates to children. Family socio-economic and psychological vulnerability are linked to parent’s education, family income and family structure. Furthermore, children of migrants and from culturally and linguistically diverse communities may experience several vulnerabilities coming from the fact that their parents do not master the language used in education institutions for everyday interactions at home, and that they are usually overrepresented amongst lower social class positions and that differences related to ethnicity might lead to disparity in treatment or even forms of segregation, at least in some countries.

There are two main and complementary approaches to evidence of early years inequalities. The first type focusses on inequalities in achievement or the extent to which children from different backgrounds are able to perform certain tasks at a certain age. The other approach focusses on inequalities in opportunities or the extent to which children from different backgrounds have different access to environments and services that relate to their development, well-being and learning.

A robust body of evidence coming from national studies documents inequalities in multiple areas of early development by children’s family backgrounds. However, international data on children’s outcomes before entry in primary education are still limited in scope and country coverage. The OECD International Early Learning and Child Well-being Study (IELS) provides data on children’s early learning through a broad scope of aspects that comprise cognitive and social and emotional development for 5-year-old children. In England (United Kingdom), Estonia and the United States – the three countries that participated in the pilot study in 2018 – socio-economically disadvantaged children had both lower early cognitive skills and social and emotional skills than advantaged children, although the strength of the relationship varies depending on the area of development (Figure 3.2).

In Europe, a study analysed the evolution of achievement gaps in children from infancy and preschool age up to end of compulsory schooling in five countries (Germany, Italy, the Netherlands, Norway, and the United Kingdom), building on national longitudinal datasets (Passaretta and Skopek (Eds.), 2018[32]). The study found evidence of gaps in achievement (e.g. in language or literacy, math and science, depending on data availability in these countries) according to several dimensions of socio-economic status and immigrant backgrounds in the early years (e.g. starting at age 2-3).

While studies on achievement gaps in the early years have progressed and have pointed to key findings, they remain limited, partly because measurement of early childhood development is complicated for several reasons. First, their age makes the assessment of young children’s development complicated. Contextual or environment factors and the state of the child at the time of the assessment influence the child’s responses, more so than for older children. Second, because early development spans across many domains and occurs at different paces, standardised assessments have been criticised for giving an incomplete picture of children’s development. Furthermore, cultural differences and differences in approaches to ECEC mean that countries put different emphases on areas of children’s development, which can contribute to differences in achievements between countries. However, these challenges also exist for measuring outcomes at older ages and have progressively been addressed as international studies have developed and their methodologies have improved. Global approaches that capture several developmental areas are better than limited ones (e.g. those looking at the number of spoken words only).

A complementary approach consists in looking at inequality of opportunity, for which there are more international data sources, although many gaps also remain in this area. For instance, in the United States, the National Academies of Sciences, Engineering and Medicine define the opportunity gap as the unequal and inequitable distribution of resources and experiences on the basis of various child characteristics (e.g. socio-economic background, race, immigrant background). This includes gaps in access to health services, quality ECEC and safe environments.

Approaches that measure early inequality of opportunity and achievement inequality need to be combined to get a better understanding of how the interplay between children and family characteristics and policies and institutions shapes achievement inequality and how this can be mitigated. For instance, the OECD Child Well-being data portal includes comparative measures on child well-being outcomes and the drivers of well-being stemming from children’s environments, although without focusing on young children specifically. This report considers both approaches.

Income inequalities translate into differences in children’s opportunities to learn and develop. There is clear evidence that higher income has a positive causal effect on maternal mental health, parenting and the quality of the home environment, and thereby influences children’s development (Cooper and Stewart, 2020[33]). Large income inequalities in a country lead to children starting their lives with different opportunities. How income inequalities evolve thereby has consequences on how differences in children’s opportunities evolve: when inequalities in family income or poverty rates increase, differences in children’s opportunities are likely to broaden as well.

Income inequality varies considerably across OECD countries (Figure 3.3). In 2022 (or latest available year), Czechia, the Slovak Republic and Slovenia had the lowest levels of income inequalities, as measured by the main indicator of the income distribution (Gini coefficient); while Chile, Costa Rica and Türkiye had the highest levels. Over the last 15 years, income inequality has remained stable on average in OECD countries, but increased in several OECD countries, including countries with low starting levels of inequality (Denmark, Hungary and Sweden) and in countries with high starting levels (Türkiye and the United States). Compared to the 1995-2010 period during which income inequalities expanded largely, inequalities have stabilised in the last 15-year period on average across the OECD (OECD, 2015[34]).

A main driver of the increase in income inequality has been a large increase in the incomes of the richest 10% (and, even more markedly, the 1%), which has been larger than the increase for the rest of the population and has therefore led to an increase in the share of the income going to the richest. This has happened in the United States but also in many other OECD countries. In the United States, some authors have argued that the economic elite is now made up of individuals who tend to have gone through successful education pathways and training, and who have a strong taste for and capacity to train their children, and who invest heavily in their children’s education through many channels (Markovits, 2019[35]). Competition for educational opportunities, coupled with high tuition fees in the private education sector, has pushed children from low-income parents out of the best schools. When high-income parents expand their children’s capacity (as discussed at the end of this chapter) in disparity with children from low-income parents, income inequality is highly likely to increase inequality of opportunity and lead to low social mobility.

At the other end of the distribution, the share of income of the poorest 10% has declined over the last three decades, as did the share of the lowest 40%, in a phenomenon of the decline of the middle class (OECD, 2019[36]). There are also large differences between countries in poverty rates (i.e. the share of the population living with less than half the median disposable income in their country) (Figure 3.4). Between 2007 and 2022, the average OECD relative poverty rate has remained stable. However, it has increased in countries with both relatively high and low poverty rates.

The link between socio-economic background and education performance is highly visible in data from the OECD’s Programme for International Student Assessment (PISA). These data measure 15-year-olds’ knowledge and skills in reading, mathematics and science, as well as their socio-economic background through the PISA index of economic, social and cultural status, which is based on questions on parents’ highest level of education, parents’ highest occupational status and home possessions. The most recent PISA data indicate that on average in OECD countries, performances of children from parents with low socio-economic status are lower than those from high socio-economic status families (Figure 3.5). Over the recent period that has been marked by a relative stagnation of inequalities, mean performance in mathematics dropped on average across OECD countries, and the socio-economic gap widened. This gap did not change significantly in the majority of OECD countries but widened in some of them. In most of these countries, these changes came from a decline in the performance of socio-economically disadvantaged students while socio-economically advantaged students’ performance did not change. Among OECD countries, the socio-economic gap in mathematics narrowed only in Chile (OECD, PISA 2022 Database, Table I.B1.5.19).

Differences in opportunities build as some children are more exposed to factors that hinder their learning, development and well-being, and are less exposed to factors that are supportive. The goal of this section is to outline the main mechanisms behind the development of early inequalities, as indicated by recent research.

The quantity and quality of parental practices (or “investment”) are widely viewed as a key determinant for children’s future economic and social success, and a source of the intergenerational transmission of human capital, and thereby an important mechanism for the reproduction of inequalities.

Three main features of parenting are important in this respect:

• Parental beliefs include what parents expect the course of development to look like and what parents see as their own role in their children’s development.

• Parenting style consists of the attitudes that parents communicate to their own children and the emotional climate in which these attitudes are expressed.

• Parenting practices cover a large domain, including the variety of interactions with their children, the kinds of home environments parents create for children, and the connections to the world outside the home that parents both enable and permit.

Parents with low socio-economic status, on average, spend less time in developmental activities with their children compared to parents with higher socio-economic status (Duncan et al., 2023[14]). This is recognised as a key driver of the transmission of inequalities. Recent evidence from United States time diary data shows that mothers with at least a bachelor’s degree spend nearly six hours more per week in direct, intensive interactions (e.g. activities such as reading, playing and bathing with their children) than do mothers with a high school degree (Kalil et al., 2023[37]). This means that over a year, the children of highly educated parents receive 300 more hours of direct parental time on average than do children of less educated parents. This represents a difference of about 10 weeks of 6-hour days of preschool between the two groups.

Survey data show gaps in the frequency of the use of stimulating practices at home between families with different socio-economic status (Figure 3.6). The Trends in International Mathematics and Science Study (TIMSS) and Progress in International Reading Literacy Study (PIRLS) surveys ask parents in a broad range of countries about the extent to which they carry out early literacy and numeracy activities with their child, such as telling stories and playing word games, or counting different things and drawing shapes. These surveys also include a measure of children’s socio-economic background through the Home Resources for Learning index, which is based on parents’ reports of the number of books at home, parents’ level of education and their highest level of occupation. In all countries, the percentage of children from advantaged socio-economic background who are regularly exposed to early literacy and numeracy activities is higher than for children from disadvantaged socio-economic background, with a gap of 21 percentage points on average in OECD countries. However, the gap varies substantively across countries, from around 10 percentage points in Czechia, Israel and the Netherlands to over 40 percentage points in Bulgaria and Türkiye.

Understanding the reasons why families from lower socio-economic status spend less time on average on rich interactions with children is important to drive policy responses. Previous research brought forward differences in the degree to which parents value or enjoy spending time in enriching activities with children, as well as in the degree to which they are informed about the importance of these interactions (Hoff, 2002[38]). However, recent studies have found limited or no support for the enjoyment hypothesis: mothers of all socio-economic levels report higher positive feelings for spending time in interactions with their children compared to other activities (Kalil et al., 2023[37]). Concerning the possible role of differences in beliefs, recent evidence suggests that parents across the economic distribution similarly understand the importance of engaging in rich interactions with their children (Duncan et al., 2023[14]). Another aspect of beliefs are the characteristics or skills that parents think they need to instil in children to prepare them for life. In the past, there seem to have been differences between parents with a high socio-economic status valuing more “independent thinking” or “self-direction”, while parents with a low socio-economic status have tended to value “obedience” and “conformity.” However, recent evidence suggests that differences in these beliefs have converged over the last three decades (Ishizuka, 2018[39]). Overall, parents with lower status seem to want to do many of the same enriching activities as those with higher status, but they are less likely to do them. In addition, studies and data on interactions between children and parents mostly rely on western notions of parental time investment, putting a strong focus on early literacy activities at home, that are not fully relevant to different population groups for which other types of activities prevail (e.g. outdoor activities, storytelling and oral traditions, dance).

In recent research, a variety of factors have been put forward to explain differences in the time spent with children by parents with different socio-economic status. Parents face different constraints that affect their decision making. Socio-economically advantaged and disadvantaged parents face differences in stress, in their social networks and in their own experiences that lead them to make different decisions (Duncan et al., 2023[14]). It has also been argued that parenting often requires quick, on-the-spot decisions and that parents make some decisions automatically, but parents with different status have different cognitive heuristics or “shortcuts”. Moreover, as parenting investments have uncertain returns, present bias can cause parents to prioritise activities involving money and time that provide immediate rather than long-term returns. Parenting in less favourable economic contexts is associated with decision making that focusses on present versus future gains and relies on habits rather than conscious problem solving. Parents with lower levels of education may be less informed about the appropriate timing of key parental inputs, in terms of child development, and about children’s developmental milestones. As a result, they may fail to promote important skills at a time when it would be most developmentally effective.

In sum, mechanisms that explain the differences in parenting practices based on socio-economic status are varied and nuanced. They are linked to differences in income, family and environmental stress and time constraints, among other factors that influence parental decisions.

Family and environmental stress affects children directly through poorer health and lower well-being, and indirectly through effects on their parents. There is consistent evidence that parents with low-socio-economic status on average interact with and invest in children to a lesser extent because they experience more stress in their daily lives than higher-income parents, both because stress increases parents’ anxiety and depression, and because it can undermine parents’ cognitive ability to focus on long-term, rather than short-term, goals (Cooper and Stewart, 2020[33]).

The Family Stress Model framework shows how poverty and economic pressures faced by low-income families, especially when coupled with other stressful events that tend to be more prevalent in these families’ lives, can create psychological distress, impact parents’ mental health and cause parental conflict and marital problems that disrupt parent-child interactions (McLeod and Kessler, 1990[40]). Stress may lower parents’ ability to acquire and process information in a way that supports their investments in their child's skill development.

Longitudinal data have enabled looking at the dynamic aspects of stress. Over time, personal distress may strain family relationships and disrupt parenting, eventually threatening the health and well-being of children living in the home (Masarik and Conger, 2017[41]). Studies have shown that depression and other forms of psychological distress (e.g. anxiety), as influenced by economic stress, are linked to: i) unsupportive parenting practices toward three-year-old children; ii) reductions in both the quality and quantity of time spent interacting with two-year-old children; iii) harsh parenting toward 6-10-year old children; iv) less provision of social and cognitive enrichment activities for 5-year-old children; v) punitive and over-controlling behaviours toward 6-year-old children; and vi) heightened risk for child abuse and neglect in the preschool years (Masarik and Conger, 2017[41]).

Exposure to stress also relates to environmental conditions. Children experience differing levels of exposure to environmental contaminants, such as lead and those that place them at risk of asthma. This is linked to housing and local environmental conditions. Furthermore, climate change creates risks of extreme weather events such as heat and flood, with risks to children’ health and feeling of home security that are related to the overall quality of the home environment. High-income parents have more resources to protect themselves and their children against these risks.

Various disciplines have studied processes of accumulation of advantages or disadvantages, either focusing on children and their families themselves (neurosciences and genetics) or children and families in relation to their broader environment (social sciences).

Children who have low cognitive scores also tend to have more behavioural problems, which suggests that there is a double disadvantage for children who lag behind their peers (Allen and Hutton, 2023[42]). The relationships between children’s well-being and their social and emotional and cognitive development, as highlighted by neurosciences research, explain these outcomes. Multiple developmental domains (i.e. cognitive, social and emotional, health) interact and affect the skill formation process over time These dynamics reinforce each other and are therefore complicated for policies to address.

Among the factors that lead to dynamics of disadvantages, research has made progress in better understanding the effects of genetics (Wang et al., 2021[43]); (Rustichini et al., 2023[44]). The role of the genetic profile of parents on children’s development means that inequalities in opportunities tend to reproduce or reinforce inequalities at birth. Parental genotype (captured by a polygenic score that predicts educational attainment) is directly transmitted to children (“direct genetic effect”), but also indirectly shapes the environment that parents provide to their children (so-called “genetic nurture”). Environments created by parents relate to their offspring’s educational outcomes independent of genetic transmission. Further, children’s genetic endowments elicit different behavioural responses from parents. For instance, genetic endowment associated with greater interest in reading steers more reading by parents to their child (Cattan, 2022[45]).

At the family level, situations that create vulnerabilities (or strengths) are interrelated. For instance, poverty can induce stress through negative environmental stimuli that are caused by violence in the family and in the community, divorces, frequent residential moves, job instability and unemployment (Shay, Shavit and Sasson, 2023[17]). These might all lead to greater use of negative parenting strategies. Cycles of disadvantages are often related to a country’s history and its legacies (e.g. racism, immigration patterns), leading to inequalities that affect some population groups in particular and that are deeply entrenched (Allen and Hutton, 2023[42]). Large ethnic gaps in opportunities exist in countries looking at this dimension (e.g. in the United States and the United Kingdom).

When inequalities in opportunities start in the pre-natal period, they often continue or expand throughout early childhood. These inequalities are influenced by a myriad of factors, including access to health care and adequate nutrition, low family income or poverty, neighbourhood safety, and environmental conditions, and are exacerbated by racism, segregation, implicit and explicit bias, and stigma.

Separations and divorces are also related to low income and family stress and lead to a decline in children’s time allocated to educational activities (e.g. studying, reading) and an increase in children’s time in unstructured activities (e.g. watching TV, video gaming, smartphone use) (Cano and Gracia, 2022[46]). In particular, separation in families with opposite-sex parents leads to a strong increase of gender inequalities in parents’ time use with father-child time remaining low or declining and mother-child time doubling. In addition, when fathers spend less time with their children, other individuals who are less committed to children’s development may spend more time with them (e.g. neighbours and nannies). A literature review that looks at estimates of causal effect of fathers’ absence finds negative effects on children’s social-emotional development, especially if father absence occurs during early childhood, and these effects are more pronounced for boys than for girls (McLanahan, Tach and Schneider, 2013[47]).

Recent research has also focussed on the role of geographic inequalities and neighbourhood effects that might lead to or reinforce inequalities in employment, income, access to services, life expectancy and well-being, and tend to create poverty traps with implications for young children (Chetty and Hendren, 2018[48]). Inequality of opportunity is thereby concentrated in some areas. Residential segregation has increased in the United States since 2000 (Heckman and Landersø, 2021[49]). Although there are large differences in the sizes of minority populations in Europe and the United States, cities experiencing recent immigrant growth have also experienced increased residential segregation, although to a lesser extent than in the United States (Lichter, Parisi and Ambinakudige, 2019[50]).

At the other end of the spectrum, socio-economically advantaged families tend to support their children in multiple ways. As already highlighted, families with a high socio-economic status stimulate children’s learning and development through more time spent in educational activities and rich interactions. They also influence child personality and behaviours through the types of interactions and values they distil in children (Hoff, 2002[38]). They are more likely to consider longer time horizon in their decision making relating to children, which might lead them to select high-quality schools and also make a range of informed decisions such as those on extracurricular activities to support children’s development in multiple areas and ensure that they benefit from rich interactions with other adults and children (Heckman and Landersø, 2022[51]).

Families with a high socio-economic status have a better understanding of the influence that the wider environment (e.g. neighbourhoods) plays in shaping childhood outcomes, in addition to other family resources (see Annex A, Workshop 1). They also have better opportunities to select their area of residence and choose those with good community-level resources and local institutions. Wealthy families are more able to choose neighbourhoods and localities with high-quality schools and peers from similar backgrounds. The effects of neighbourhoods on child development have received considerable attention in recent economics research (Chetty and Hendren, 2018[48]). Families with high education levels and income tend to move to rich neighbourhoods with similar families comprising their community, while families with low education and income are pushed towards poorer neighbourhoods. Such residential sorting has been increasing over the past decades in some countries, including the United States.

Studies have shown that high-SES families are more likely than other families to compensate for their children’ difficulties in the early years. For instance, some authors have found that families with highly educated mothers provide more support to low birth weight children (compensatory effect) while families with lesser educated mothers provide less support to these children (reinforcing effect) (Restrepo, 2016[52]). This can be explained by budget constraints or differences in awareness of how to compensate for different endowment at birth. Families with high socio-economic status are also more likely to look for health and social services to address health problems and detect special education needs.

Some researchers have seen the compound effects of the factors discussed in these sections as resulting in diverging life paths for children depending on their socio-economic backgrounds (McLanahan, 2004[53]). Family behaviours increasingly concentrated at lower levels of socio-economic status include nonmarital childbearing, divorce, early childbearing, multi-partner fertility, and unintended childbirth, whereas those increasingly concentrated at higher levels of socio-economic status include later childbearing, stable employment, stable marriage, and more involvement of fathers in childrearing. Socio-economic bifurcation in family behaviour is thought to contribute to growing inequality and reproduction of inequalities (McLanahan, 2004[53]).

[42] Allen, L. and R. Hutton (eds.) (2023), Closing the Opportunity Gap for Young Children, National Academies Press, Washington, D.C., https://doi.org/10.17226/26743.

[1] Bendini, M. (2022), Quality Early Learning: Nurturing Children’s Potential, World Bank, Washington, DC.

[2] Bethlehem R.A.I., S. (2022), “Brain charts for the human lifespan”, Nature, Vol. 604/7906, pp. 525-533, https://doi.org/10.1038/s41586-022-04554-y.

[46] Cano, T. and P. Gracia (2022), “The Gendered Effects of Divorce on Mothers’ and Fathers’ Time with Children and Children’s Developmental Activities: A Longitudinal Study”, European Journal of Population, Vol. 38/5, pp. 1277-1313, https://doi.org/10.1007/s10680-022-09643-2.

[45] Cattan, S. (2022), “Early childhood inequalities”, IFS Deaton Review of Inequalities.

[31] Cerna, L. et al. (2021), “Promoting inclusive education for diverse societies: A conceptual framework”, OECD Education Working Papers, No. 260, OECD Publishing, Paris, https://doi.org/10.1787/94ab68c6-en.

[22] Chaput, J. et al. (2017), “Systematic review of the relationships between sleep duration and health indicators in the early years (0–4 years)”, BMC Public Health, Vol. 17/S5, https://doi.org/10.1186/s12889-017-4850-2.

[48] Chetty, R. and N. Hendren (2018), “The Impacts of Neighborhoods on Intergenerational Mobility I: Childhood Exposure Effects*”, The Quarterly Journal of Economics, Vol. 133/3, pp. 1107-1162, https://doi.org/10.1093/qje/qjy007.

[7] Colliver, Y. et al. (2022), “Free play predicts self-regulation years later: Longitudinal evidence from a large Australian sample of toddlers and preschoolers”, Early Childhood Research Quarterly, Vol. 59, pp. 148-161, https://doi.org/10.1016/j.ecresq.2021.11.011.

[33] Cooper, K. and K. Stewart (2020), “Does Household Income Affect children’s Outcomes? A Systematic Review of the Evidence”, Child Indicators Research, Vol. 14/3, pp. 981-1005, https://doi.org/10.1007/s12187-020-09782-0.

[11] Delgado, H. et al. (2024), “Differential psychophysiological responses associated with decision‐making in children from different socioeconomic backgrounds”, Child Development, https://doi.org/10.1111/cdev.14082.

[32] Dublin, T. (ed.) (2018), Roots and Development of Achievement Gaps: A Longitudinal Assessment in Selected European Countries, ISOTIS Report.

[14] Duncan, G. et al. (2023), “Investing in early childhood development in preschool and at home”, in Handbook of the Economics of Education, Elsevier, https://doi.org/10.1016/bs.hesedu.2022.11.005.

[19] Ferrari, P. (ed.) (2010), “Timing of Intervention Affects Brain Electrical Activity in Children Exposed to Severe Psychosocial Neglect”, PLoS ONE, Vol. 5/7, p. e11415, https://doi.org/10.1371/journal.pone.0011415.

[10] Fox, S., P. Levitt and C. Nelson III (2010), “How the Timing and Quality of Early Experiences Influence the Development of Brain Architecture”, Child Development, Vol. 81/1, pp. 28-40, https://doi.org/10.1111/j.1467-8624.2009.01380.x.

[18] Frankenhuis, W. and A. Gopnik (2023), “Early adversity and the development of explore–exploit tradeoffs”, Trends in Cognitive Sciences, Vol. 27/7, pp. 616-630, https://doi.org/10.1016/j.tics.2023.04.001.

[5] Ginsburg, K. (2007), “The Importance of Play in Promoting Healthy Child Development and Maintaining Strong Parent-Child Bonds”, Pediatrics, Vol. 119/1, pp. 182-191, https://doi.org/10.1542/peds.2006-2697.

[25] Grippo, A. et al. (2023), “Indoor air pollution exposure and early childhood development in the Upstate KIDS Study”, Environmental Research, Vol. 234, p. 116528, https://doi.org/10.1016/j.envres.2023.116528.

[51] Heckman, J. and R. Landersø (2022), “Lessons for Americans from Denmark about inequality and social mobility”, Labour Economics, Vol. 77, p. 101999, https://doi.org/10.1016/j.labeco.2021.101999.

[49] Heckman, J. and R. Landersø (2021), Lessons from Denmark about Inequality and Social Mobility, National Bureau of Economic Research, Cambridge, MA, https://doi.org/10.3386/w28543.

[24] Herrmann, M., K. King and M. Weitzman (2008), “Prenatal tobacco smoke and postnatal secondhand smoke exposure and child neurodevelopment”, Current Opinion in Pediatrics, Vol. 20/2, pp. 184-190, https://doi.org/10.1097/mop.0b013e3282f56165.

[4] Hirsh-Pasek, K. et al. (2008), A Mandate for Playful Learning in Preschool, Oxford University Press, https://doi.org/10.1093/acprof:oso/9780195382716.001.0001.

[38] Hoff, E. (2002), “Socioeconomic status and parenting”, in Handbook of parenting: Vol. 2. Biology and ecology of parenting.

[39] Ishizuka, P. (2018), “Social Class, Gender, and Contemporary Parenting Standards in the United States: Evidence from a National Survey Experiment”, Social Forces, Vol. 98/1, pp. 31-58, https://doi.org/10.1093/sf/soy107.

[37] Kalil, A. et al. (2023), Education Gradients in Parental Time Investment and Subjective Well-being, National Bureau of Economic Research, Cambridge, MA, https://doi.org/10.3386/w31712.

[28] Kildare, C. and W. Middlemiss (2017), “Impact of parents mobile device use on parent-child interaction: A literature review”, Computers in Human Behavior, Vol. 75, pp. 579-593, https://doi.org/10.1016/j.chb.2017.06.003.

[23] Kurdziel, L., K. Duclos and R. Spencer (2013), “Sleep spindles in midday naps enhance learning in preschool children”, Proceedings of the National Academy of Sciences, Vol. 110/43, pp. 17267-17272, https://doi.org/10.1073/pnas.1306418110.

[15] Lansford, J. et al. (2023), “The HOME-21: A revised measure of the home environment for the 21st century tested in two independent samples.”, Psychological Assessment, Vol. 35/1, pp. 1-11, https://doi.org/10.1037/pas0001183.

[50] Lichter, D., D. Parisi and S. Ambinakudige (2019), “The Spatial Integration of Immigrants in Europe: A Cross-National Study”, Population Research and Policy Review, Vol. 39/3, pp. 465-491, https://doi.org/10.1007/s11113-019-09540-3.

[6] Loebach, J. et al. (2021), “Paving the Way for Outdoor Play: Examining Socio-Environmental Barriers to Community-Based Outdoor Play”, International Journal of Environmental Research and Public Health, Vol. 18/7, p. 3617, https://doi.org/10.3390/ijerph18073617.

[30] Ma, K. (2022), “The Role of Family Socioeconomic Status in Parenting Styles and Practices”, in Proceedings of the 2022 International Conference on Science Education and Art Appreciation (SEAA 2022), Atlantis Press SARL, Paris, https://doi.org/10.2991/978-2-494069-05-3_4.

[35] Markovits, D. (2019), The Meritocracy Trap, Penguin Press.

[41] Masarik, A. and R. Conger (2017), “Stress and child development: a review of the Family Stress Model”, Current Opinion in Psychology, Vol. 13, pp. 85-90, https://doi.org/10.1016/j.copsyc.2016.05.008.

[53] McLanahan, S. (2004), “Diverging destinies: How children are faring under the second demographic transition”, Demography, Vol. 41/4, pp. 607-627, https://doi.org/10.1353/dem.2004.0033.

[47] McLanahan, S., L. Tach and D. Schneider (2013), “The Causal Effects of Father Absence”, Annual Review of Sociology, Vol. 39/1, pp. 399-427, https://doi.org/10.1146/annurev-soc-071312-145704.

[40] McLeod, J. and R. Kessler (1990), “Socioeconomic Status Differences in Vulnerability to Undesirable Life Events”, Journal of Health and Social Behavior, Vol. 31/2, p. 162, https://doi.org/10.2307/2137170.

[3] Ministère des Solidarités et de la Santé (2020), Les 1000 premiers jours: Là où tout commence, Ministère des Solidarités et de la Santé, Paris.

[16] Nolvi, S. et al. (2023), “Prenatal Stress and the Developing Brain: Postnatal Environments Promoting Resilience”, Biological Psychiatry, Vol. 93/10, pp. 942-952, https://doi.org/10.1016/j.biopsych.2022.11.023.

[12] Norman, H. (2023), What a difference a dad makes. Paternal Involvement and its Effects on Children’s Education (PIECE) study, Leeds: University of Leeds.

[27] OECD (2023), Empowering Young Children in the Digital Age, Starting Strong, OECD Publishing, Paris, https://doi.org/10.1787/50967622-en.

[13] OECD (2021), Starting Strong VI: Supporting Meaningful Interactions in Early Childhood Education and Care, Starting Strong, OECD Publishing, Paris, https://doi.org/10.1787/f47a06ae-en.

[36] OECD (2019), Under Pressure: The Squeezed Middle Class, OECD Publishing, Paris, https://doi.org/10.1787/689afed1-en.

[34] OECD (2015), In It Together: Why Less Inequality Benefits All, OECD Publishing, Paris, https://doi.org/10.1787/9789264235120-en.

[29] Radesky, J. et al. (2015), “Maternal Mobile Device Use During a Structured Parent–Child Interaction Task”, Academic Pediatrics, Vol. 15/2, pp. 238-244, https://doi.org/10.1016/j.acap.2014.10.001.

[52] Restrepo, B. (2016), “Parental investment responses to a low birth weight outcome: who compensates and who reinforces?”, Journal of Population Economics, Vol. 29/4, pp. 969-989, https://doi.org/10.1007/s00148-016-0590-3.

[44] Rustichini, A. et al. (2023), “Educational Attainment and Intergenerational Mobility: A Polygenic Score Analysis”, Journal of Political Economy, Vol. 131/10, pp. 2724-2779, https://doi.org/10.1086/724860.

[8] Schlesinger, M. et al. (2020), “Cognitive Behavioral Science behind the Value of Play: Leveraging Everyday Experiences to Promote Play, Learning, and Positive Interactions”, Journal of Infant, Child, and Adolescent Psychotherapy, Vol. 19/2, pp. 202-216, https://doi.org/10.1080/15289168.2020.1755084.

[17] Shay, D., Y. Shavit and I. Sasson (2023), “Poverty in early childhood and future educational achievements”, Early Child Development and Care, pp. 1-14, https://doi.org/10.1080/03004430.2023.2236803.

[21] Sutton, P. and G. Darmstadt (2013), “Preterm Birth and Neurodevelopment: A Review of Outcomes and Recommendations for Early Identification and Cost-effective Interventions”, Journal of Tropical Pediatrics, Vol. 59/4, pp. 258-265, https://doi.org/10.1093/tropej/fmt012.

[20] Tong, S. et al. (2024), “Novel insights from our special issue on maternal factors during pregnancy that influence maternal, fetal and childhood outcomes”, BMC Medicine, Vol. 22/1, https://doi.org/10.1186/s12916-024-03278-2.

[26] UNICEF (2023), Breathless beginnings: the alarming impact of air pollution on children in Europe and Central Asia.

[43] Wang, B. et al. (2021), “Robust genetic nurture effects on education: A systematic review and meta-analysis based on 38,654 families across 8 cohorts”, The American Journal of Human Genetics, Vol. 108/9, pp. 1780-1791, https://doi.org/10.1016/j.ajhg.2021.07.010.

[9] World Health Organization (2019), Guidelines on physical activity, sedentary behaviour and sleep for children under 5 years of age, World Health Organization.