Woman must be less than 22 weeks pregnant to participate

The Vitamins in Pre-eclampsia trial is looking for 2,400 women to take part: so far, more than 500 have signed up.

The volunteers will take vitamin C and E supplements to see whether that could help prevent the disorder.

Pre-eclampsia can result in the early delivery of the baby and high blood pressure for the mother.

Peter Soothill, professor of fetal and maternal medicine at St Michael's Hospital, told the BBC: "It is not entirely understood what causes this.

"Some women are more likely to get it - particularly those who had it in a previous pregnancy."

Southmead Hospital is also involved in the research.

Women eligible for the study must live in the UK and be less than 22 weeks pregnant.

They must have had pre-eclampsia in their last pregnancy, or have a medical condition which would make them more likely to get pre-eclampsia.