Ecological association between operative vaginal delivery and obstetric and birth trauma.

Background: Increased use of operative vaginal delivery (use of forceps, vacuum or other device) has been recommended to address high rates of cesarean delivery. We sought to determine the association between rates of operative vaginal delivery and obstetric trauma and severe birth trauma.

Methods: We carried out an ecological analysis of term, singleton deliveries in 4 Canadian provinces (2004-2014) using data from the Canadian Institute for Health Information. The primary exposure was mode of delivery. The primary outcomes were obstetric trauma and severe birth trauma.

Results: Data on 1 938 913 deliveries were analyzed. The rate of obstetric trauma was 7.2% in nulliparous women, and 2.2% and 2.7% among parous women without and with a previous cesarean delivery, respectively, and rates of severe birth trauma were 2.1, 1.7 and 0.7 per 1000, respectively. Each 1% absolute increase in rates of operative vaginal delivery was associated with a higher frequency of obstetric trauma among nulliparous women (adjusted rate ratio [ARR] 1.06, 95% confidence interval [CI] 1.05-1.06), parous women without a previous cesarean delivery (ARR 1.10, 95% CI 1.08-1.13) and parous women with a previous cesarean delivery (ARR 1.11, 95% CI 1.07-1.16). Operative vaginal delivery was associated with more frequent severe birth trauma, but only in nulliparous women (ARR 1.05, 95% CI 1.03-1.07). In nulliparous women, sequential vacuum and forceps instrumentation was associated with the largest increase in obstetric trauma (ARR 1.44, 95% CI 1.35-1.55) and birth trauma (ARR 1.53, 95% CI 1.03-2.27).

Interpretation: Increases in population rates of operative vaginal delivery are associated with higher population rates of obstetric trauma, and in nulliparous women with severe birth trauma.