A study of interest to midwives has found that almost two-thirds of women who attempt a natural delivery after a previous Caesarean section are successful, while 37% require an emergency Caesarean.
It revealed that 63% managed a vaginal delivery with their second baby, while the remainder needed an emergency operation to deliver their child.
The team, led by Hannah Knight, from the Royal College of Obstetricians and Gynaecologists (RCOG), published its findings in BJOG: An International Journal of Obstetrics and Gynaecology.
Its study, which excluded women with known medical complications such as diabetes, is one of the biggest to examine natural delivery among women who had their first baby by Caesarean.
It found that 52% of 143,970 women attempted a vaginal birth after a Caesarean section (Vbac). All had their first baby by Caesarean between 2004 and 2011.
Younger women (aged 24 or under) were found to be more likely to attempt Vbac than women aged over 34, while black and Asian women were also found to have higher Vbac attempt rates for their second delivery compared with white women.
Between 20% and 25% of all UK births are by Caesarean section. The reason for the first C-section was found to strongly determine the likelihood of successful natural delivery in the second pregnancy.
Women whose first labour required an induction which then failed were almost twice as likely to have a failed Vbac.
The team also discovered variation in the rate of attempted and successful Vbac between NHS trusts.
There was almost a threefold variation in attempted Vbac (ranging from 33% to 94%) and almost a twofold variation in successful vaginal delivery for the second baby (between 48% and 84%).
Consultant obstetrician Tahir Mahmood said the findings showed the majority of women were successful, but risks were higher among women who have had a previous Caesarean section.
Dr Mahmood, who worked on the study, said one in 200 women would experience a rupture of their scar. Other risks included a tendency for the baby to experience more foetal distress.
Lead researcher Miss Knight said most women with an uncomplicated first Caesarean section are candidates for attempting Vbac, but data found that only half of those women chose this option.
She added: “An informed discussion about whether or not to attempt a vaginal delivery after a Caesarean section requires an assessment of the risk of emergency Caesarean, and this paper provides valuable information both for women and the obstetricians and midwives caring for them.”
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