Almost Two-Thirds of Attempted VBACs Are Successful, Study Finds


Most women who attempt a vaginal birth after cesarean are successful, but the reason for the first cesarean strongly determines the outcome of an attempted VBAC.

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

The study, conducted by the Office for Research and Clinical Audit (ORCA) at the Royal College of Obstetricians and Gynaecologists and the London School of Hygiene & Tropical Medicine, aimed to investigate the factors that determine the uptake and success rate of vaginal birth after cesarean.

The data from 143,970 women, who had their first baby by cesarean section between 2004 and 2011, showed that just over half (52%) attempted a vaginal birth after cesarean section (VBAC) for their second baby.

Researchers found that younger women, aged 24 years or less, were more likely to attempt a VBAC than women older than 34 years (60% vs 45%, respectively). Black women (62%) and Asian women (64%) also had higher VBAC attempt rates for their second delivery when compared with white women (49%).

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

The reason for the first cesarean section was also found to strongly determine the likelihood of successful natural delivery in the second pregnancy. Furthermore, women with a history of failed induction of labor were almost twice as likely to have a failed VBAC.

The researchers also found variation in the rate of attempted and successful VBAC between NHS trusts. There was almost a 3-fold variation in attempted VBAC, ranging from 33% to 94%, and almost a 2-fold variation in successful vaginal delivery for the second baby, between 48% and 84%.

"The majority of women with an uncomplicated first cesarean section are candidates for attempting VBAC, but our data found that only half of those women chose this option,” said Hannah Knight, Office for Research and Clinical Audit, Royal College of Obstetricians and Gynaecologists, and lead researcher of the paper. “Women from a non-white ethnic background were more likely than white women to attempt a VBAC, but the success rate in non-white women was lower. This could point to different patient preferences or a lack of access to elective repeat cesarean section for non-white women.”

"Interestingly, we also found an unexplained variation in the rate of attempted and successful VBAC between hospitals, which was independent of maternal demographic and clinical risk factors,” Miss Knight added.

She concluded, "An informed discussion about whether or not to attempt a vaginal delivery after a caesarean section requires an assessment of the risk of emergency cesarean, and this paper provides valuable information both for women and the obstetricians and midwives caring for them."

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