Maternal Stress and Cognitive Delay: Vivette Glover

Maternal Stress and Cognitive Delay: Vivette Glover

1. How did you become interested in the effects of stress on fetal and child development?

Well, I originally was trained as a biochemist, then I became interested in biological psychiatry. Then it so happened that I was working in a maternity hospital, so I started to be interested in the biological and psychological aspects of pregnant women. And then we found that the most interesting aspect of that was the effects of the mother's mood in pregnancy on the development of the fetus and the child.

2. What is your current area of research?

There's really more and more evidence that the emotional state of the mother while she's pregnant affects the development of her fetus including the brain, with a long term effect on the child's neurodevelopment. But there were, and still are, quite a lot of outstanding questions. So, the research I've been presenting here -- is that what you would like to know about? -- the research I've been presenting here is about a new study we've been doing where we were asking several questions. We wanted to know more firmly that the effects we were finding were due to the effects on the fetus which lasted onto the child. We wanted really distinguish whether the effects were prenatal or postnatal. And we wanted to understand more about the mechanisms. So we wanted to understand more about what it might be about the in utero environment that affected the child's outcome.

So, we recruited women who were having amniocentesis. And then if the children turned out well and healthy full term, which most of them did, we invited the mother and child to come back when the child was about one and a half. And we asked the mother about the stress she'd experienced during pregnancy, and the stress she'd experienced postnatally. And we looked at two outcomes for the child: we looked at their cognitive development, like a baby IQ test, and also their emotional development, particularly how fearful they were. And what we found was really quite clear cut. We found that if the mother was stressed while she was pregnant, this had a marked effect on the cognitive development of the child. It also increased the likelihood of the child being fearful, to a fearful inducing stimulus. And if we looked at the postnatal stress, there was nothing like this comparable effect. And if we looked at one allowing for the other, the effects were really mainly what were happening to her in pregnancy. So, I think this provides even stronger evidence that stress, if the mother is stressed while she's pregnant, does affect the neurodevelopment of the child. Then we also had the in utero hormone exposure, particularly cortisone, and we found that if the cortisone levels were higher in utero, this correlated with a less well development IQ, the child at 18 months. So, we’re just beginning to get at the mechanism and, of course, cell exposure in the womb looks a likely part of this mechanism.

3. Does stress experienced during labor and delivery have a negative impact on child development?

Yes, I mean it's less stressful for the baby to be born by cesarean, particularly elective cesarean, than by normal delivery, or particularly in an assisted delivery, like forceps. And we've followed the child up really only in the first few months, and if they had a more stressful delivery, they had bigger cortisol stress responses later. But we don't how long that persists. It maybe a factor, but I don't think if it is a factor that's anything like as strong as this exposure throughout pregnancy.

4. How does the timing of maternal stress affect fetal development?

And in this study we didn't address that, but in previous studies and other studies people have looked at that, and the answers aren't very consistent. I think that probably what's going on depends on which outcome we're looking at. We know that stress in pregnancy really affects quite a few different outcomes. It can effect the cognitive development, the emotional development, can increase the risk for ADHD. And the systems in the brain that are controlling these different outcomes are maturing at different stages in pregnancy. So it may well depend on exactly which outcome you're looking at, which gestational age is most sensitive, but we need to do lots more work to understand that.

What we do know is it's not all over by the first trimester. Often people think that in pregnancy you have to be particularly careful at the beginning with thalidomide and so on, but that's when the limbs are forming, when the growth structures are developing. But the brain is developing all the way through. In fact, it's developing more in the second half of pregnancy. So, on the evidence such as it is suggests that it's probably later in pregnancy that there's more vulnerability, but as I say we need to do much more to understand that better.

5. Is there a link between prenatal exposure to stress and developmental disorders in children?

Well, we know that if a mother is stressed while she is pregnant it increases the risk for a range of different disorders. It's not specific. But it's not the same children that are affected in different things than are one. There's rather low correlation between how much they were affected for their cognitive development or their anxiety reactivity. Um, again, we need lots more research to understand this better, but I think it's highly likely there's a gene environment interaction, and if the child is more vulnerable to say becoming fearful then the exposure to more stress in pregnancy will bring out that problem. If they're more vulnerable to cognitive delay, it could bring out a different problem. So, they're non-specific effects, or at least there's a broad range of effects, but the effects are different depending on the individual child. It may also be the gestational age of exposure. We don't know. But we do know that the clinical magnitude of these effects is quite substantial, and we calculated about 15% of the attributable load for ADHD is due to prenatal stress. And for a range of problems we're looking at, I think it's about that sort of amount if the variance is accounted for that. So that means that if one could reduce the stress of the mother while she is pregnant, one could prevent a really significant proportion of developmental disorders occurring.

6. What were the most common sources of stress in your participants?

Well, we found two sorts. One was if the mother had suffered or was suffering from mental illness, or had a close relative that was suffering from mental illness. But the other that emerged from the study very strongly was stress due to her relationship with her partner. And if she said that her partner was emotionally cruel to her or they had frequent rouse and arguments, or her partner and she had separated, these had a big impact on the child's cognitive development. And that's really new. That isn't already in the literature, and I was really quite surprised by the magnitude of these effects. How this sort of relationship strain impacted on the child development.

7. What research findings most surprised you?

How well it turned out I suppose. The magnitude of the effect, because our total cohort was a 125, and I thought when we setout that might be a bit small. But the effects were so substantial they were very statistically significant with this size group.

8. Are there strategies that women can use to reduce anxiety and stress during pregnancy?

> That's really where the research needs to go, because we need to understand more about how to intervene and a way to help appropriately. There haven't been any studies in pregnancy specifically designed to address this, but we do know from outside pregnancy a lot of psycho-therapeutic methods can help reduce anxiety, for example, or stress or help with the relationship. Cognitive behavioral therapy can help. Interpersonal therapy can help. So, I think that we need to, women themselves need to, be aware that if they're feeling this way they should get help. Talking to anybody can help. So, they need to see someone who can help them, and try and get help. And then, there haven't really been proper studies of things like yoga or other methods of relaxation which one might think could help. They certainly won't do any harm, but they need to be evaluated.

9. Did you consider any other maternal factors besides stress in your study?

> We had information about how much they smoked, how much they drank. They actually smoked and drank very little. They were fairly educated group, not a socially deprived group. And they didn't have very many of the other sorts of factors that you think might contribute. So, we allowed for that, but we didn't actually get effects for that.

10. Where do you see your research heading in the future?

Well there are many. We'd like to know more about how long these effects persist. These children were only 18 months, so we want to follow them up and see if this persists throughout childhood and even into adulthood. From other research I think it's highly likely they will, but we need to know how much they do. We want to understand more about the correlates with the brain structure; we'd like to do brain imaging.

The other factors that could interact, such as diet. There's some reason to think that the type of diet can affect these outcomes, new research just starting. And there could well be interactions between prenatal stress and type of diet.

All the research so far in this area has been done in developed countries. I think there are big implications for other countries, the developing world where the women may be exposed to much more stress. Also in places like Iraq; when I see the news pictures of what's going on in Iraq I think of the pregnant women and what's happening for their children. So, we need to, I mean I think that we need to understand more of that and be aware that in political situations of great trauma you're not only affecting the current generation, but probably the future generation. And then as well as all that, of understanding that, understanding more about the mechanisms. We’ve looked at cortisol, just the beginning of understanding the biology of how the mothers’ change of mood transmits itself to the fetus. We need to understand more about that. And then probably most important of all, we need to actually study intervention and see which are the most appropriate interventions, and see that we can actually help the mothers in a way that's going to help their outcome for their children.