Stress during pregnancy harms a foetus

When an animal is pregnant the developing baby exchanges nutrients and waste products through its umbilical cord and placenta, which attaches to the wall of the mother's uterus. But, if the mother is exposed to stress the placenta works less well, which can affect the growth of the baby, as Cambridge University's Owen Vaughan explained to Danielle Blackwell...

Owen - The aim of the study was to look at how glucocorticoids, which are a stress hormone secreted both in the mother and the foetus, what happens when they're raised during pregnancy. What we found was that when these glucocorticoid levels are raised in the pregnant mother, the ability of the placenta to transport glucose to the foetus is reduced.

Danielle - How did you conduct the study?

Owen - So, the study used mice. The mice were given corticosteroid in their drinking water for 5 days. We then used a tracer technology to measure the amount of glucose passing across the placenta.

Danielle - What direct effects did this have on the foetus?

Owen - The foetus itself was smaller at the time we conducted the study which was towards the end of pregnancy. In humans, being a smaller baby, puts you first of all had greater risk of complications in the immediate postnatal period. But also, increases your life-long risk of metabolic disease or things like type 2 diabetes and obesity.

Danielle - You mentioned in your paper that some of the mice given the stress hormone were overeating. How does this affect the amount of glucose that then can pass through the placenta?

Owen - The glucocorticoid treatment also increased the amount of food that the animals ate each day. But what we found was that if we prevented them from overeating, we no longer saw the changes in the ability of the placenta to transport glucose. So clearly, there's an interaction between the two on stress levels and nutritional intake.

Danielle - Is it possible that we can then remove some of the harmful effects to the foetus by controlling their diet instead of maybe controlling the stress hormones?

Owen - What this might mean is that we can limit the effects of stress on the foetus by manipulating the maternal diet. So that for any particular stress hormone profile, there might be a most appropriate diet for the mother during pregnancy.

Danielle - So far, all this work has been carried out in mice. Do you see this applying to humans? Is there a similar mechanism that happens in humans with elevated stress hormone levels, do we think?

Owen - Well, certainly glucocorticoids are sort of a central signal of many different sorts of stress. In humans, they are raised in response to more psychosocial stresses but also, things like nutrient deprivation.

Danielle - Is this something that we could possibly then use as a drug target if there are mothers that are going through prolonged periods of stress and have prolonged elevated stress hormone levels? Is this something that maybe we can therapeutically target to remove these adverse effects?

Owen - In particular, we found that when the stress hormone levels are high in the mother, the expression of a particular gene called red1 in the placenta is increased. So, if we can somehow alter the way that responds to stress or nutrients in the mother, we might have a way of protecting placental function from changes in the material environment.