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Two profound changes over recent decades have produced a dramatically altered landscape for early childhood in many countries (Phillips and Shonkoff, 2000). First, research reviewed in this chapter has advanced our understanding of early development. Second, there have been changes in the social and economic circumstances in which families with young children are living: (1) work patterns of parents with young children; (2) high levels of economic hardship among families; (3) increasing cultural diversity and the persistence of significant racial and ethnic disparities in health and developmental outcomes; (4) growing numbers of young children spending considerable time in childcare settings; and (5) greater awareness of the negative effects of stress on young children. Britto et al. (2017) collated the findings of many thousands of studies on the characteristics of nurturing care in a systematic review (see Box 3.2).

Early environmental experiences can have a lasting impact on a child’s later success in school and life more generally. It has been claimed that differences in the size of children’s vocabulary first appear at 18 months of age, based on whether they were born into a family with high education and income or low education and income (Hart and Risley, 1995). By age 3, children with college-educated parents or primary caregivers have vocabularies two to three times larger than those whose parents had not completed high school. Unless they are engaged in a language-rich environment in early life by school age, children are already behind their peers.

Adverse living circumstances impair a child’s development in the first 24–36 months of life, and the greater the degree of adversity, the greater the odds of developmental delay. Risk factors include poverty, caregiver mental illness, child maltreatment, single parenthood and low maternal education, which can collectively have a cumulative impact. Maltreated children who are exposed to up to six additional risks face a 90–100% likelihood of having one or more delays in their cognitive, language or emotional development (Barth et al., 2008).

BOX 3.2 Nurturing care: promoting early childhood development

Advances in basic and intervention science indicate that early childhood is a period of special sensitivity to experiences that promote development, and that critical time windows exist when the benefits of early childhood development interventions are amplified.

The most fundamental promotive experiences in the early years of life come from nurturing care and protection received from parents, family and community, which have lifelong benefits including improved health and wellbeing, and increased ability to learn and earn.

Nurturing care and protection are supported by a range of interventions delivered pre-pregnancy and throughout birth, the newborn period, infancy and early childhood. Many of these interventions (centred around the areas of parenting support, attachment and bonding, breastfeeding, micronutrients and child feeding, prevention of child maltreatment and out-of-home interventions) have shown benefits for child development, nutrition and growth, and reductions in morbidity, mortality, disability and injury.

Interventions that integrate nurturing care and protection can target multiple risks to developmental potential at appropriate times, and can be integrated within existing preventive and promotive packages.

Preventive and promotive packages can build on existing platforms, such as community-based strategies and social safety nets, for delivering parental and child services at scale to vulnerable and difficult-to-reach populations, enhancing their effectiveness and sustainability.

Source: Britto et al. (2017: 91). Reproduced by permission

Early experiences can actually get ‘under the skin’ and have life-long effects on cognitive and emotional well-being, and on long-term physical health as well. Significant childhood adversity is a predictor of adult health problems, including diabetes, hypertension, stroke, obesity and some forms of cancer. Adults who recall having seven or eight serious adverse experiences in childhood are three times more likely to have cardiovascular disease as an adult (Dong et al., 2004).

Future Research

1 The developmental model of the origins of chronic disease suggested by Barker and others offers an important alternative approach to disease prevention based on the provision of nurturing care and the protection of the foetus and neonate. Economic studies of the benefits of early life prevention versus the traditional approach, which targets adult lifestyle change, are needed to inform policy and prevention.

2 Improved understanding of the epigenetic mechanisms of early life development, especially those associated with the initial critical phases, will make it possible to design effective interventions.

3 The ethical and legal implications of epigenetic embryonic forecasting need to be studied so that guidelines can be devised prior to implementation.

4 There is a need for more research to validate the GWAS approach and to examine the reasons for the high amounts of missing heritability.

Summary

1 Humans have 23 pairs of chromosomes, and thus a total of 46 chromosomes. One copy of each chromosome is inherited from the female parent and the other from the male parent. Chromosomes are made of protein and a single molecule of deoxyribonucleic acid (DNA), which contains the instructions making each human being unique.

2 It is necessary to distinguish between a person’s genotype and phenotype. The genotype is the part of the individual’s genetic makeup that determines their potential characteristics. The phenotype is the observable characteristics of an individual resulting from the interaction of the genotype with the environment.

3 Nature and nurture are of equal importance in determining human abilities and character. However, the relative proportions of influence can differ from a 50:50 split for specific functions and characteristics. Nature is more important for structural and anatomical differences, while nurture has greater influence on psychological and social differences.

4 Epigenetics is the study of heritable changes caused by mechanisms other than changes in the underlying DNA sequence. The epigenetic inheritance system has been described as ‘soft inheritance’ because it is amenable to adaptation to fluctuations in environments, such as changes in nutrition, stress and toxins.

5 The ‘Foetal Origins Hypothesis’ of David Barker proposed that undernutrition in utero and during infancy permanently changes the body’s structure, physiology and metabolism, causing coronary heart disease and stroke in adult life.

6 Orthodox thinking about chronic disease suggests that it results from adult lifestyles and genetic inheritance. The developmental model of the origins of chronic disease suggested by Barker and others offers an important alternative approach to disease prevention based on the provision of nurturing care and the protection of the foetus and neonate.

7 Breastfeeding has clear short-term benefits for child health, reducing mortality and morbidity from infectious diseases, encouraging healthy food preferences and promoting the establishment of a healthy gut microbiome.

8 Stress exposures of parents may occur before conception, at the time of conception, at the time of pregnancy, or in the early postnatal period. Children of mothers who are exposed to poverty, hunger, poor diet, smoking, stress, war or violence prenatally are prone to epigenetic influences on their offspring’s later well-being.

9 Maltreatment during childhood is associated with reduced volume of both the midsaggital area and the hippocampus, the two brain regions involved in learning and memory. Epigenetic changes in the CNS may be responsible for observed delays in cognitive development.

10 Children who receive inadequate care, especially in the first 24 months of life, are more sensitive to the effects of stress and display more behavioural problems than children who receive nurturing care.