Factors associated with obstetric anal sphincter injuries during vacuum delivery among Chinese women.

OBJECTIVE

To investigate factors associated with obstetric anal sphincter injuries (OASIS) during vacuum delivery among Chinese women.

METHODS

A retrospective cohort study of Chinese women who underwent vacuum-assisted vaginal delivery at a tertiary referral hospital in Taiwan between January 2010 and December 2016. Logistic regression analysis was used to compare various factors (maternal, delivery, and neonatal factors) between women with and those without OASIS.

RESULTS

Among 18 744 Chinese women with singleton vaginal delivery, 3141 (16.76%) had vacuum assistance and 2634 (83.86%) were primiparous. Of the women who had a vacuum delivery, 1073 (34.16%) sustained OASIS, of whom 967 (90.12%) were primiparous. The major independent risk factors for OASIS were primiparity (adjusted odds ratio [aOR], 2.93; 95% confidence interval [CI], 2.29-3.76) and use of midline episiotomy (aOR, 3.01; 95% CI, 1.74-5.17). However, epidural analgesia had a protective effect (aOR, 0.64; 95% CI, 0.54-0.75) against OASIS. In multivariate analysis for the primiparous subgroup, the independent significant risk factors for OASIS remained the same.

CONCLUSION

A high incidence of OASIS during vacuum delivery was observed among Chinese women. Midline episiotomy was found to be a modifiable risk factor for OASIS, whereas epidural analgesia had a protective effect.