Pre-eclampsia is also a greater risk among women in their first pregnancy with a BMI over 30.
Experts studied 385 such women and found that 11.7% of them developed pre-eclampsia compared with 6% of obese women with one or more previous pregnancies and only 2% of the average population. They also found that the risk of pre-eclampsia increased as BMI increased.
Lead researcher Professor Lucilla Poston said: "The high number of cases of pre-eclampsia found in this group was very concerning, as this is a serious pregnancy complication which, in extreme cases, can result in maternal and/or foetal death.
"We must now start to consider first-time pregnancy as an additional problem in obese pregnant women, who we know are already more likely than thinner women to have a complicated pregnancy."
The study was funded by the baby charity Tommy's, the Wellcome Trust and the Biomedical Research Centre at Guy's & St Thomas' NHS Foundation Trust - and published in the American Journal of Obstetrics and Gynaecology.
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