Perineal trauma with vaginal birth after a previous caesarean section: A retrospective cohort study.

BACKGROUND: There is a paucity of information regarding perineal injuries in women who achieve vaginal birth after caesarean section (VBAC).

AIMS: To ascertain the rate of severe perineal injuries in women achieving VBAC at a major tertiary obstetric hospital, and to determine if vaginal birth is more likely to be associated with perineal injuries in women with one previous caesarean section compared with nulliparous women.

MATERIALS AND METHODS: A retrospective cohort study was undertaken of women with singleton pregnancies at term who delivered vaginally between 2013 and 2016. We compared nulliparous women with women who had undergone one previous caesarean section. The primary outcome analysed was the rate of third and fourth degree tears in each group. Secondary outcomes were major post-partum haemorrhage and instrumental delivery.

RESULTS: Totals of 10 663 nulliparous women and 629 VBAC women achieved vaginal birth. Of the VBAC women, 418 achieved their first vaginal birth (first VBAC group). Overall, there was no significant difference in the rate of third and fourth degree tears in the VBAC group compared with the nulliparous group (6.0% vs 5.6%; P = 0.73). There was no significant increase in anal sphincter injuries in the first VBAC group compared with the nulliparous group (6.0% vs 7.4%; P = 0.25).

CONCLUSION: No overall difference in the rate of severe perineal injuries between VBAC women and nulliparous women who achieve vaginal birth was observed in this study.