Is stress good or bad for the developing foetus? According to Sue Gerhardt, It depends on the type of stress. Chronic and intense stress may be damaging. Babies exposed to their mother’s cortisol are found to be born more irritable and prone to crying. Moderate levels of stress may help the nervous system to develop (cognitive and motor functions). But even low-level stress can have a negative impact on the emotional systems. For mothers living in poverty or working long hours this may put strain on the foetus. A mother working long hours, particularly in the early stages of pregnancy can impair the growth of the foetus leading to a lower birthweight. Very low birthweights can lead to health problems later in life.
The amygdala is at the centre of the brain’s emotional reactions and is involved in triggering the stress response. It is formed by 15 weeks of pregnancy. When the amygdala is exposed to high levels of cortisol, particularly early in the pregnancy, it responds by growing larger and growing more connections to other parts of the brain. Prenatal stress can also decrease the size of the hippocampus which plays an inhibiting role on the amygdala. Research on rats show it reduces connections in the prefrontal cortex.
A mother who has high levels of anxiety or depression in late pregnancy is more likely to have a baby that finds it hard to cope with stress and takes longer to get over stress. Highly anxious mothers are more likely to have children that grow up to have ADHD symptoms and behavioural problems.
A story is told of the Patagonian culture in South America where women are treated like royalty when they are pregnant. She is awakened to the sound of beautiful music. She is entertained and amused in ways that fit with her particular tastes. She takes gentle exercise like walking. Just as a sound tree produces good fruit, the Patagonians recognised that the future well-being of the society rested upon the mother being well-cared for in pregnancy.
Important emotional regulators are being established before the baby is born. Neurotransmitters like the dopamine and serotonin systems are already being programmed. These influence the development of the amygdala and the stress response. The brain is formed by building on what is built before. The developments laid down during pregnancy become the foundation on which later development will build. Even small things can set the organism off on a different developmental path. It can also be hard to undo these early developments. The foetus is also picking up on the cultural conditions while in the womb – Is this a loving and nourishing culture it is being born into? Or do they need to prepare for conditions of hardship and deprivation?
Our early experiences help develop our relational and emotional ways of being. The experiences in this time are the hidden emotional history of each person, that remains hidden but central throughout our lives. During babyhood patterns of relating are wired into our bodies and brains. This period has been referred to as ‘unrememberable and unforgettable’ – we cannot consciously remember these experiences but they manifest in our expectations and behaviour.