London - Mothers put themselves at higher risk when trying a natural birth following a caesarean, according to a major study.
The women are seven times more likely to suffer a ruptured womb and have a slightly greater risk of potentially deadly sepsis.
The Oxford University study of more than 74 000 births found their babies have a marginally higher risk of needing resuscitation or dying during or after birth.
Dr Kathryn Fitzpatrick, who led the research, said: "Our findings can be used to counsel and manage women with previous caesarean sections and should be considered alongside existing evidence on the increased risk of serious maternal morbidity in subsequent pregnancies associated with elective repeat caesarean section."
Nearly 30 percent of women who give birth have a caesarean section. For their second pregnancy most are given the choice of a caesarean or a natural delivery.
Women given a C-section have their baby removed through an incision and the scarring can tear in childbirth. This ruptures the womb, which can cause severe bleeding for mothers and, in a very small number of cases, the death of their baby. However fewer than two percent of women who attempt a natural birth after a caesarean suffer complications.
Professor Andrew Shennan, a consultant obstetrician and representative of the charity Tommy’s, said: "The increased risk of attempting a vaginal birth after a caesarean is slightly greater overall compared to an elective caesarean.
"But the risk of these complications is the same as for women giving birth for the first time, and therefore reasonable. There are also advantages to avoiding repeated C-sections."
Doctors say that repeated caesareans carry the risk of infection or damage to the bladder or bowel from the surgical incision.
The Oxford researchers examined the cases of 74 043 women who gave birth in Scotland between 2002 and 2015 – after at least one previous caesarean.
More than 28 000 planned to give birth naturally, with more than two thirds managing to do so without needing an emergency caesarean. Another 45 579 women opted for a planned caesarean.
The study, published in the journal PLOS Medicine, found women attempting a natural birth were 7.3 times more likely to suffer a ruptured womb. This happened to 69 women in this group compared with 17 women among those having a repeat caesarean.
They were also more likely to see their babies die during or after birth, need resuscitation or neonatal care, or be born unwell based on the apgar scale, which rates babies’ health.
The extra danger for babies may be caused by women suffering ruptured wombs, or the stress of being pushed through the birth canal.
Their mothers were 80 percent more likely to suffer sepsis, which can be caused by bacteria when women’s membranes rupture after going into labour. However the risk was small.