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The impact of stress on the developing foetus

Watch this video. Professor Jane Barlow describes some of the mechanisms that mean stress during pregnancy can have long-lasting consequences.
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In this section we’re going to be thinking about the impact of stress on the developing foetus. The prevalence of common mental health problems in the antenatal period is high. Antenatal stress is common, with as many as 20% of women experiencing symptoms of anxiety in pregnancy. Both anxiety and depression in pregnancy are associated with postnatal depression. Many women also experience other problems in pregnancy that are strongly associated with anxiety and depression. For example, around 30% of domestic abuse starts during pregnancy and around 9% of women are being abused during pregnancy or after giving birth. Around 1% of pregnancies in the UK involve a drug-dependent mother.
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And such drug dependency co-occurs with a range of other problems, including psychiatric disorder and particularly disorders related to emotional regulation. Adverse prenatal mental health has been shown to be associated with a wide range of compromised outcomes for the baby, both in the short term, such as immediately following the birth, and in the longer term through to adolescence and adulthood. We’ve known for a very long time, for example, that very severe stress can have an impact on physical aspects of the unborn baby’s development.
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For example, research shows that in the first trimester, the death of an older child was associated with an increase in congenital malformations, while less severe forms of stress were associated with low birth weight and reduced gestational age and an altered sex ratio with fewer males to females being born than in an unstressed population. However, more recent studies have also begun to identify an impact on a range of aspects of the child’s neurodevelopmental and socioemotional functioning. For example, a number of studies have identified an impact of maternal stress in pregnancy on the neurodevelopmental functioning of newborn babies, including an increase in fearfulness and difficult temperament, sleep problems and lower cognitive performance.
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Studies that have examined the association between prenatal stress and neurodevelopmental outcomes in children aged 3 to 16 years show an increased risk of child emotional problems, especially anxiety and depression, and symptoms of attention deficit and hyperactivity disorder and conduct disorder. Other studies have shown a reduction in cognitive performance associated with prenatal stress. So what might the mechanisms for this be? Although we don’t currently fully understand the mechanisms that may underlie foetal programming by prenatal stress in humans, a number of potential pathways have been identified. One early suggestion was a decrease in blood flow to the foetus as a result of the increased stimulation by cortisol of the mother’s sympathetic nervous system.
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This in turn was thought to cause increased constriction of her blood vessels, which reduced uteroplacental blood and reduced oxygen and calorie intake for the foetus. However, more recent research has suggested that a more likely mechanism that has been identified in animal models only involves the foetus being overexposed to cortisol as a result of maternal cortisol crossing the placenta. A number of studies have shown that maternal stress can influence the transfer of cortisol across the placenta as a result of changes to the barrier enzyme which converts cortisol to the inactive cortisone.
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High levels of cortisol can be toxic for the foetal brain and can adversely affect a number of areas of both foetal and child brain, including the HPA axis, which is responsible for setting the stress thermostat and results in these children experiencing higher levels of stress throughout childhood into adulthood. Increased serotonin is another possible mediator of prenatal stress on the neurocognitive and behavioural development of the baby. In humans, stress during pregnancy caused by violence from the partner has also been shown to cause epigenetic changes in the DNA in the blood of their adolescent children.
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In the next video, I talk to Vivette Glover, who is Professor of Perinatal Psychobiology at Imperial College London and we explore some of these issues in more detail. The supporting article and the video provides you with the opportunity to learn more about the impact of stress in pregnancy. Please also share your thoughts about this section of the course in the discussions.

The mother’s emotional mind in pregnancy may alternate between feelings of happiness and relaxation, and other less optimal feelings such as anxiety and depression.

Anxiety during pregnancy is common, and in this video we describe some of the research that has been conducted over the last decade, and what it tells us about the impact of stress on the developing foetus. We focus in particular on research that has examined the impact of such stress on the neurobehavioural and psychological functioning of the baby and the child.

We also describe some of the mechanisms by which this occurs, focusing in particular on new research which suggests that stress may affect the ability of the placenta to prevent the transfer of cortisol from the mother to the foetus, and the impact of this on the rapidly developing foetal nervous system, and in particular their Hypothalamic Pituitary Adrenal axis (HPA), which plays a role in setting the infant’s stress thermostat.

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Babies in Mind: Why the Parent's Mind Matters

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