Research by leading Australian scientists has found that what is ‘learned’ both in the womb and throughout the first few years of life has profound consequences over the course of a life.
The First Thousand Days1 has shown children are affected in multiple ways, including through biology, their experiences, environment and diet, and their parent’s health and lifestyle during pregnancy.
Most fascinating however is that starting from conception, the foetus is actively responding to changes in the environment, using cues provided by the mother’s physical and mental state to ‘predict’ the kind of world they will be born into and altering their bodily structures accordingly.
First Thousand Days lead author Dr Tim Moore says this adaptation can be either beneficial or detrimental, depending on the child’s relationships and environments.
“Children need to feel calm, safe and protected. When this attachment process is interrupted, the child’s brain places an emphasis on developing neuronal pathways that are associated with survival, before developing those that are essential to future learning and growth.”
The role of epigenetics and synaptic pruning
The science describes two central mechanisms that underlies this adaptation process: epigenetics (whereby the genes listen to the environment) and synaptic pruning (whereby the brain listens to the environment).
What this means is that our genes alone do not determine our characteristics but work in tandem dynamically with our environments. When this occurs the result is epigenetic change.
A child may have a combination of genes that predisposes them to a particular condition or behaviour, but never be exposed to the particular environment needed to trigger this condition so the gene remains dormant. Similarly, a child may be exposed to a particular triggering environment, but lack the genes that would predispose them to respond adversely.
The paper states that epigenetic changes have been implicated in the development of a wide range of disorders, from cardiovascular disease to autism spectrum disorders and cognitive disorders, and may be triggered by a wide range of environmental exposures and experiences.
In humans, the epigenetic system is most sensitive to environmental influences during the period of developmental plasticity (i.e. the first 1000 days).
The periods before and just after fertilisation are highly sensitive periods. Epigenetic changes can start to occur shortly after conception.
The research found that at conception, the egg and sperm combine their genetic material to form an embryo, whose set of genes reflects both the age and the environmental exposures of both parents.
“During fertilisation and the first cell divisions, the embryo is highly sensitive to signals from the mother’s reproductive tract: the fluid that surrounds the embryo during its passage to the womb varies according to the mother’s nutritional, metabolic, and inflammatory states, reflecting the particular world in which she lives. The embryo has a high degree of developmental plasticity, and responds to these environmental cues by modulating its metabolism, gene expression, and rate of cell division.
"Epigenetic changes can occur throughout pregnancy. Hormones and nutrients that cross the placenta can be affected by the mother’s body composition, metabolism, and long-term lifestyle.
“The foetus is sensitive to hormonal and other physiological indicators of maternal stress, and heightened exposure to stress in the womb is associated with greater reactivity to stress after birth, as well as longer-term problems with emotional and cognitive functioning.
“In general, prenatal stress exposure makes children more reactive to challenge and threat. In addition, maternal stress and toxin exposure during pregnancy, and maternal-infant interactions after birth have been linked to changes in the offspring’s epigenetic state.
“Even natural variations in the quality or quantity of maternal care can have a long-term impact on the offspring’s brain and behaviour. The prevalence of these effects suggests that epigenetic effects are a central mechanism by which environmental experiences, both positive and negative, become biologically embedded and ‘get under the skin’.”