Genes from both parents can increase the risk of Preeclampsia, a serious complication that occurs in about 5 percent of pregnancies, doctors said on Friday.

After studying data on 500,000 births, researchers at the University of Bergen found that the mother and father can pass on a susceptibility to their children.

“Men and women who were born after preeclamptic pregnancies contribute to increased risk of Preeclampsia in the next generation,” said Professor Rolv Skjaerven, of the department of public and primary health care.

Dangerously high blood pressure, fluid retention and protein in the urine are symptoms of Preeclampsia. It can lead to eclampsia, which endangers the lives of both mother and child.

Eclampsia, in which Preeclampsia symptoms worsen and the patient begins to have seizures, is one of the most common causes of death for pregnant women in the developing world.

Scientists knew mothers could pass on the risk of the condition to daughters born after pregnancies affected by it.

But the research, published online by the British Medical Journal, shows that mothers who are affected by Preeclampsia pass on a higher risk to all their daughters, including those born following normal pregnancies.

“If a sister or brother has Preeclampsia when they were born, an unaffected sister will have almost the same risk,” Skjaerven explained in an interview.

He and his team found that daughters of women who had Preeclampsia during pregnancy had more than twice the normal risk of having the complication. Men born after a Preeclampsia pregnancy had a raised risk of having a daughter who would suffer from the problem.

Doctors do not know what causes Preeclampsia, which can starve the developing foetus of nutrients. The condition usually occurs after the 20th week of pregnancy.

It is also more common in first and twin pregnancies. Treatment of Preeclampsia consists of monitoring the mother and early delivery of the baby, usually by caesarean section.

Dutch scientists have identified a genetic defect that is a suspected cause of Preeclampsia. The defective gene is linked to an enzyme that clears toxic compounds in the body.