The rising rate of Caesarean deliveries is putting more women and babies at risk when they have a second child.

Those mothers who try to have their second child naturally are 50 times more likely to suffer a ruptured womb during childbirth if they have previously had a Caesarean, research suggests.

If this happens, the lives of both mother and baby can be threatened, and about one in 20 babies will die.

The risks are even greater among women over 35, or if the second birth is induced, the study of more than 300,000 births in Sweden has found. There are about 120,000 Caesareans performed in NHS hospitals in England and Wales every year. There are no figures for how many women go on to try for a normal vaginal birth the next time, but it has become more common in recent years.

Since an increasing number of women giving birth are older, or have had Caesareans first time round, particular care is needed to ensure that they are properly counselled about the risks, say the authors of the new study, led by Melissa Kaczmarczyk of Emory University in Atlanta, Georgia.

Virginia Beckett, a consultant obstetrician and gynaecologist at Bradford Teaching Hospitals Foundation Trust, said the figures found in the Swedish study reinforced advice already given in Britain. She said: “One important thing is that we should ensure that the Caesarean rate doesn’t rise any higher. In some units it is now as high as 30 per cent of births.”

The new figures, published in BJOG, an International Journal of Obstetrics and Gynaecology, come from a study of 300,200 Swedish women who gave birth between 1983 and 2001.

The study found that almost a quarter of women attempting a normal birth after a Caesarean required a second Caesarean. Mothers over 34 were nearly three times as likely to suffer a ruptured womb than were those under 25. Those with a body mass index (BMI) of 30 or over (clinically obese) were more than twice as likely to experience uterine rupture than those with a BMI under 25 (normal).

Belinda Phipps, chief executive of the National Childbirth Trust, said: “The absolute risk of rupture is very small. We have to try very hard to get the first labour right.Then the problem doesn’t arise.”

— Pauline Williams, a driving instructor from Ebbw Vale in Wales, suffered a rupture of the womb when giving birth to her third child in 2004, having had a previous Caesarean. She survived, but her daughter, Nia, was born with brain damage and died later. Earlier this year Gwent Healthcare NHS Trust agreed an out-of-court settlement after Mrs Williams said she had not been warned fully of the risks.

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