Women's perineal outcomes in births attended by registered and student midwives across stages of the 30-birth training requirement: An Australian cohort study

Abstract

Perineal trauma, including obstetric anal sphincter injury (OASI), is a significant adverse outcome of vaginal birth. Although perineal care skills are acquired during midwifery clinical placement, limited evidence examines whether student involvement or stage of preregistration experience influences perineal outcomes. Aim To examine whether perineal outcomes differ between spontaneous vaginal births in which a supervised student midwife was recorded as the primary accoucheur and births attended by a registered midwife, and to assess whether OASI risk varies across stages of preregistration student experience. METHODS: This retrospective cohort study included term, singleton, cephalic spontaneous vaginal births across three public hospitals in New South Wales, Australia (2018�2024). Cohort A comprised all eligible births attended by registered midwives or student midwives (n = 34,235). Cohort B included postgraduate student midwives with complete ascertainment of 30 student-attended births (n = 3930), categorised as ? 10, 11�20 and 21�30 births. Modified Poisson regression with robust variance estimation was used to estimate risk ratios (RRs) for OASI. RESULTS: In Cohort A, student midwife involvement was not independently associated with OASI (aRR 1.07, 95% CI 0.93�1.22). In Cohort B, experience category was not associated with OASI risk in the overall adjusted model. However, compared with the ? 10 birth group, the 21�30 birth group demonstrated a higher adjusted OASI risk (aRR 1.61, 95% CI 1.02�2.55), while no difference was observed for the 11�20 birth group. CONCLUSIONS: Student midwife involvement was not associated with OASI risk. A modest increase in risk in the highest experience group warrants further investigation. Perineal outcomes were more strongly influenced by maternal and intrapartum factors than by cumulative birth exposure.