The researchers found that women with low levels of the mineral raised their risk of developing the condition by up to four times.
Pre-eclampsia can develop in late pregnancy and causes high blood pressure, damage to the kidneys and reduced blood flow to the placenta that can complicate the pregnancy. It is not yet understood how the condition begins but the team from the University of Surrey writes in November's issue of the American Journal of Obstetrics and Gynecology (vol 189, no 5) that the reduction in selenium status in some countries over recent years could be contributing to the condition.
Research published last year found that selenium levels in British bread-making wheats are 10 to 50 times lower than in their American or Canadian counterparts and that bread made from such wheat would fail to help consumers meet the recommended intake of the mineral. It is thought that reduced pollution may be partly to blame along with a general deficiency of selenium in UK soils.
Selenium acts as a powerful antioxidant and free radical scavenger and has been associated with reduced risk of prostate, bladder and skin cancers.
In the new study, researchers measured selenium from the toenails of 53 preeclamptic patients and 53 matched pregnant controls at the John Radcliffe Hospital in Oxford. They found that average toenail selenium concentrations in the pre-eclamptic subjects were significantly lower than in their matched controls.
Being in the bottom tertile of toenail selenium was associated with a 4.4-fold greater incidence of the condition. And within the pre-eclamptic group, lower selenium status was significantly associated with more severe expression of disease (measured by delivery before 32 weeks), reported the scientists. Pre-eclampsia affects around 5-8 per cent of all pregnancies, according to the Preeclampsia Foundation.
The findings raise the question of whether supplementing selenium levels could reduce risk of pre-eclampsia, write the team. Selenium is currently not available in supplement form in many European countries but the incoming European directive on food supplements will allow the mineral to be sold in all member states.