Science Interviews


Sun, 19th Jul 2009

Stress During Pregnancy

Professor Vivette Glover, Imperial College London

Listen Now    Download as mp3 from the show Making Babies - Fertility and Pregnancy

Vivette -   Well, weíre interested in how the emotional state of the mother during pregnancy affects the development of the foetus or the future child and what weíre finding is that quite a wide range or different sources of stressors; the motherís more anxious, she has quarrels with her partner, can affect fetal development.

Photograph of abdomen of a pregnant womanMeera -   So, how have you gone about looking in to this?

Vivette -   Well, we recruit pregnant women and we ask them all sorts of questions about themselves, quite often we ask them to fill in questionnaires or we interview them.  So, we find out different aspects of their emotional state.

Meera -   So what effect does their emotional state have on their foetus?

Vivette -   Well, we then follow up the child and what we find is that thereís quite a wide range of different effects it can have on the child.  It could increase the risk of symptoms of Attention Deficit Hyperactivity Disorder, ADHD, can increase the childís level of anxiety, it can have an effect on their learning abilities, so they have a lower IQ and it can make them have a high level of conduct disorder of generally being hard to control.  Different children are affected in different ways.  So, we think this is probably an interaction with their genetic vulnerability.  So, say if they are genetically vulnerable to anxiety that increases the risk of them becoming anxious children.

Meera -   And so, what is the actual connection between this so what happens as a result of the mother of being stressed to then have this effect on the baby?

A pregnant womanVivette -   Were looking into that at the moment, the evidence that there are certain effects is very good.  The evidence about the mechanisms is only just starting.  But one of the things we think is probably involved is the stress hormone cortisol and we have some evidence that if the mother is stressed, this affects the function of her placenta which usually filters what passes from the mother to child, it is usually a very effective barrier to cortisol, but if sheís anxious more cortisol passes to the child.  So, we think thatís part of the mechanism.  The placentaís function is affected and the foetus is exposed to more cortisol and that changes the development of the foetal brain.

Meera -   Itís thought that the increase in the amount of cortisol reaching the baby could be perhaps be to do with an enzyme that isnít functioning quite correctly, is that right?

Vivette -   Thatís right what we think is happening is that the placenta usually has a very high level of the enzyme that breaks down cortisol and it has been shown in animals, and we are just studying now because we think itís probably happening in humans, that the enzyme gets whatís called down regulated, it becomes less effective, so the barrier to cortisol becomes weaker, more cortisol goes through the placenta, but weíre studying on that right now.

Meera -  Well now, as part of your stand here at the Royal Society, youíve actually got some human placentas on show.  So I must admit itís very intriguing to look at.  So, could you take me through this placenta?

Vivette -   Well, this was delivered about a week ago.  Weíve got it encased safely in a vacuum-packed bag bit like you might get meat in the supermarket so you can see the actual structure of the placenta, you can see the cord, you can see the foetal side and the maternal side.

Meera -   Thatís quite a difference in colour between the foetal and the maternal side.

Vivette -   Yes, the placenta is actually made from the foetus and you might not know that the placenta has a sex.  So, if the foetus is male the placenta is male and actually, male and female placentas behave in different ways.

Meera -   How do they behave differently?  What do they do?

Vivette -   Weíll, weíre just starting to look at that, but for example, if the mother has asthma, the response of the placenta is quite different whether itís a male or female placenta.

Meera -   And so, this difference in the male and female placenta, could that change if the mother is then stressed, so could that then have a different effect on the child?

Human placentaVivette -   Thatís one of the things weíre looking into right now, which has been shown in the animals, so there are quite big differences in how baby girls and baby boys are affected by prenatal stress and so, weíre looking to see if thatís happening in humans as well.

Meera -   And just lastly I guess, what is it about this increase in cortisol entering the child that has an affect on the child?  What does it do to a baby?

Vivette -   Well it does a lot of things.  It causes it to grow more slowly, so it can help to contribute to the baby, being born small for its gestational age, but it also affects how the brain develops.  It depends on the time of exposure but different bits of the brain, the part of the brain that controls fear or controls memory come to be developed in different ways because itís exposed to high levels of cortisol.

Meera -   And so once this is fully understood, is this just going to increase advice for mothers to basically trying to stay stress free?

Vivette -   Well I think that should be part of whatís more generally known in society.  Mothers thereís a limit to how much they can do for themselves and I think, they should be advised to try and look after themselves and take time off and relax.  But I think itís also very important there should be more help given to pregnant mothers.  I think the physical care in our country of pregnant women is very good.  The emotional care of pregnant women has hardly started and I think if we could provide more emotional support, the appropriate kind, depending what the problem is, we could help the outcome and health, not just of the mother but of her child as well.


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