Don't mix stress with pregnancy
A recent survey shows that if mothers suffer stress in pregnancy it can affect their baby’s health in years to come, writes ANTHONY KING.
EXPECTANT MOTHERS should try to reduce stress and not just for their own sakes. A mother’s emotional health can affect her baby for years to come, according to recent research, so stress should be avoided along with cigarettes and alcohol.
But future mothers need help. “Everyone ought to be cherishing pregnant women more,” says Prof Vivette Glover, an expert on prenatal studies at Imperial College London.
Her research has linked emotional stress during pregnancy to behavioural and developmental problems in children. She emphasises that fathers have a significant role to play in reducing stress in mothers-to-be, as do family and friends.
Her studies revealed that the 15 per cent most anxious women in a large study group had double the rate of children with attention deficit hyperactivity disorder (ADHD). Another found that if a mother said she was stressed during pregnancy her child was more likely to perform poorly on baby IQ tests or to be more fearful. Of the millions of children in Britain and Ireland with some form of developmental disorder, perhaps 10-15 per cent could be due to the effects of prenatal stress, say the researchers at Imperial.
Many of the findings come from a study that recruited 15,000 women in Bristol in 1990-91 and followed them and their children to this day.
Glover looked at which life events were most serious during pregnancy. Mental illness in the mother or friends or family was one. “But the relationship with her partner was another,” she says. “If they said their partner had been emotionally cruel to them, which several did, then that was a very strong risk factor for the child having behavioural problems later.”
She says fathers often feel excluded during pregnancy, but they have a big role to play by making their partner’s pregnancy as calm as possible. “Stress from a bad relationship with the father is really serious in this area.”
The question of why stress can impair the development of an unborn child is being tackled by Kieran O’Connell from Co Mayo, now a doctoral student at Imperial College London.
O’Donnell studied psychiatry in London but became fascinated by foetal programming and its biology. He is studying children in the Bristol group at age 11 and plans to look at them as teenagers in a future study. At the Royal Society Summer Science Exhibition in London this year, O’Donnell showed visitors a human placenta, encased in plastic, and explained his research.
“The placenta is a fascinating and neglected organ. We’re showing it because not many people know what it looks like,” he said. “It’s not the most beautiful thing but its function is quite something. The placenta provides nourishment and air for the foetus for nine months, but it also blocks out the majority of the stress hormone cortisol.”
Though the mechanisms for the effects of stress on the human foetus are unclear, studies in lab animals suggest cortisol has a major role.
Cortisol is released when animals are stressed and can kill nerve cells in the hippocampus area of the brain, important for learning and memory, explains Glover. “In monkeys, if the mother is stressed, the hippocampus is smaller.”
Prenatal stress in animals affects memory and learning ability in their offspring, and scientists can reproduce such effects by giving synthetic cortisol to lab animals. Glover’s work – still in its early stages – now seeks to understand the implications of such findings for people.
Usually an enzyme in the placenta breaks down 90 per cent of the cortisol coming from the mother. “We’ve found that the more anxious a mother is while waiting for amniocentesis, the greater the link between the level of her cortisol and the cortisol in the amniotic fluid,” says Glover.
“We think that the mother’s emotional state has an effect on the leakiness of the placenta to cortisol,” she explains, “so that stress breaks down the protective barrier. This in turn affects the development of the foetal brain, which can impact on intelligence and behaviour.”
Reassuringly, not all women are affected and not all children. It’s important to emphasise that we are dealing with the top 10-15 per cent most anxious women, says O’Donnell. “And different children are affected in different ways: the child that was more fearful wasn’t also the child with the lower IQ, for example.”
Glover says: “It’s quite noticeable that children are affected in different ways and most aren’t affected at all. We think it’s a gene-environment interaction.” So if you are genetically vulnerable and then you are stressed, the symptoms may appear.
Glover says physical care of pregnant women has improved enormously in the past 100 years but emotional care has not. She believes GPs are not fully aware of the impacts of stress.
But it’s not all over at birth, says Glover, and the early environment of a child has a long-term effect. “We’re starting to show that sensitive mothering can reverse some of the negative effects,” she says.
“Sometimes you just can’t help life. Stresses will happen. So we think it is quite positive that we can intervene during the postnatal period,” adds O’Donnell.
The researchers also note that prenatal depression is more prevalent in some of their studies than postnatal depression.
What should women do to help themselves and their baby? “They shouldn’t push themselves too much and should take time off when they can,” advises Glover. “They should talk to other people about any problems, because talking helps a lot.”
But why does a stressed mum produce a hormone – cortisol – that may impair her baby’s future? Two of the major effects of prenatal stress in terms of behaviour are decreased attention, which in humans is ADHD, and increased anxiety, which is associated with increased vigilance, says Glover.
Raising awareness about stress is vital, says O’Donnell: “The nine months of pregnancy are some of the most important months of our life. There are huge rates of growth and development in every organ and structure and we should do whatever it takes to ensure that development reaches its full potential. Reducing stress is one thing we can do.”