London School of Hygiene & Tropical Medicine

Almost two-thirds of women who attempt a natural delivery after having a caesarean section for their first birth are successful, according to a new study published in BJOG: An International Journal of Obstetrics and Gynaecology.

The study, conducted by the London School of Hygiene & Tropical Medicine and the Office for Research and Clinical Audit at the Royal College of Obstetricians and Gynaecologists, looked at the factors that determine the uptake and success rate of vaginal birth after caesarean.

A study of 143,970 women who had their first baby by caesarean section between  2004 and 2011 found that just over half (52%) attempted a vaginal birth after caesarean section (VBAC) for their second baby. Younger women aged 24 or less were more likely to attempt a VBAC than women aged over 34 (60% vs 45%, respectively). Black women (62%) and Asian women (64%) were also more likely to attempt a VBAC for their second delivery than white women (49%).

Of the women who attempted a VBAC, about two-thirds (63%) had a successful natural delivery, though researchers found that black women had a particularly low success rate when compared to white women (50% vs 66%, respectively).  The study also showed that women aged over 34 had a lower success rate than women aged 24 or less (59% vs 69%, respectively).

The reason for the first caesarean section was also found to strongly determine the likelihood of successful natural delivery in the second pregnancy. Women with a history of failed induction of labour were almost twice as likely to have a failed VBAC than women without such a history. 

The researchers also found 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 (48% to 84%).

Study co-author Dr David Cromwell , Senior Lecturer at the London School of Hygiene & Tropical Medicine, said: “Most women who have an uncomplicated caesarean section for their first child are candidates for attempting a trial of labour for their second baby.  In England, around 50,000 women each year are faced with this decision, but it was unclear how many had been choosing to have a trial of labour. 

“This study found around half of these women in England chose this option, and about two-thirds had a successful vaginal delivery.  We also found that women who underwent an elective caesarean section in their previous pregnancy were more likely than other women to attempt VBAC, and these women also had a higher rate of success.  We hope the study results will help clinicians to provide guidance on trial of labour after caesarean section.”

Current UK guidelines state pregnant women with a primary c-section and uncomplicated healthy second pregnancy should be given the option of a vaginal birth for their next baby, or an elective-repeat c-section, and counselled on the risks and benefits of both.

Publication

• Knight HE, Gurol-Urganci I, van der Meulen JH, Mahmood TA, Richmond DH, Dougall A, Cromwell DA. Vaginal birth after caesarean section: a cohort study investigating factors associated with its uptake and success. BJOG. DOI: 10.1111/1471-0528.12508.