Genetic clues to pre-eclampsia

Certain combinations of maternal and fetal genes might increase the risk of pre-eclampsia, the most common serious complication of pregnancy, UK scientists say.

The researchers, based at Cambridge University, think some genetic variations that affect the mother's immune system could influence the supply of nutrients to the developing fetus. The findings, published in the Journal of Experimental Medicine, could eventually lead to a screening test to identify pregnant women at risk of the condition, say the team.

Pre-eclampsia usually arises during the second half of pregnancy. It can cause high blood pressure, liver problems, blood abnormalities, slow fetal growth and, if untreated, can lead to life-threatening seizures in the mother. Because the only way to 'treat' pre-eclampsia is to deliver the baby, the condition is a major reason for premature births and their associated health problems. The causes of pre-eclampsia are unknown, although some scientists think that it could be triggered by the mother's immune system attacking the fetal cells that form the placenta. The condition runs in families, suggesting that genes are involved, but other factors are also thought to play a role.

In the latest study, the researchers looked at DNA from 200 pregnant women who had pre-eclampsia and 201 expectant mothers who did not have the condition. They focussed on a gene that makes a key immune system protein, called KIR, which is crucial to setting up the placenta's blood supply. In a healthy pregnancy, fetal cells called trophoblasts do this by 'invading' the uterus, while communicating with maternal immune cells. The scientists found that women who had two copies of the 'A' version of the KIR gene had an increased risk of pre-eclampsia, but only if a particular genetic variation affecting a protein on the surface of the fetal trophoblast cells was also present.

The study suggests that genetic factors could trigger pre-eclampsia, by causing a 'communication breakdown' between the mother's cells and the fetal cells that make the placenta. Team leader Ashley Moffett stresses that 'miles more research is needed', but adds that 'this is the first hint that certain gene combinations between the mother and the baby will make some women at risk'. Mike Rich, of the charity Action on Pre-Eclampsia, welcomed the research, telling BBC News Online that 'the development of a test which could identify those women more at risk would have a significant effect on the management of pre-eclampsia'.