Women who were underweight when they were born are at greater risk of severe pre-eclampsia in pregnancy, a Swedish study involving 6,000 women suggests.

The risk is particularly pronounced if their mothers had pre-eclampsia when pregnant with them, researchers say.

Pre-eclampsia is a common condition which causes high blood pressure and can put the mother's life at risk.

UK experts said doctors should use the findings, reported in BJOG, to identify women who need more careful monitoring.

The researchers looked at more than 6,000 women under the age of 30 years who had been unusually small when they were born and who had given birth themselves.

Women who were underweight when born had a "markedly increased" risk for severe pre-eclampsia during their pregnancy, they said.

If their mothers had also had pre-eclampsia, the risk was doubled.

The research supports previous work suggesting that pre-eclampsia may run in families.

Low birth weight is also believed to be related to other conditions associated with high blood pressure, such as heart disease.

Prevention

Spotting pre-eclampsia early on can be difficult, despite routine monitoring of blood pressure, and knowing who might be more at risk would be useful.

Dr Karin Zetterstrom, study leader and gynaecologist and obstetrician at Orebro University Hospital in Sweden, said pre-eclampsia could be dangerous to a mother and baby in many ways.

"Those who are born underweight also have high risk of heart disease and the severe form of pre-eclampsia might be part of that pathway.

"It might be of value to ask a woman if she was born underweight or if her mother had pre-eclampsia because we know she is at high risk that her pre-eclampsia will turn out to be the severe form."

Professor Andrew Shennan, professor of Obstetrics and Gynaecology at King's College London and spokesperson for the baby charity Tommy's, agreed with the researchers recommendations for identifying and monitoring those at increased risk.

He said finding women at risk of the severe form of the condition was key.

"One of the really important things is distinguishing between early (commonly severe) and late onset pre-eclampsia because early onset is where the problems lie.

"But paradoxically we don't see people very often at that crucial time and that's the time we need increased surveillance."

"This is quite new stuff and a lot of obstetricians may not even be thinking about it," he added.

Professor Phil Steer, BJOG editor-in-chief, said: "What this research demonstrates is the need for careful and detailed history taking when a woman is first seen in pregnancy.

"If we know that the likelihood of a woman developing severe pre-eclampsia is high, increased surveillance during pregnancy and early appropriate management will help to safeguard the health of both mother and baby."