Risk of perinatal mortality in the first year of midwifery practice in New Zealand: analysis of a retrospective national cohort

OBJECTIVES: To determine whether there was an increased risk of perinatal mortality among mothers booked for care with community lead maternity carer (LMC) midwives in their first compared with later years of practice. DESIGN: Retrospective cohort study using linked national maternity, mortality and workforce data; adjusted analysis using logistic regression. SETTING: New Zealand. PARTICIPANTS: Women under community LMC midwifery care birthing 2008–2014. MAIN OUTCOME MEASURES: Perinatal mortality (stillbirths and neonatal deaths of babies born from 20 weeks’ gestation to the 27th day of postnatal life), excluding terminations and deaths associated with congenital abnormalities. RESULTS: There were 2045 deaths among 344 910 births booked with midwives. First year of practice midwives cared for women with higher risk of perinatal mortality, including Māori, Pacific, Indian, <20-year-old mothers, nullipara, smokers, women living in socioeconomic deprivation and with high body mass index, than midwives beyond first year of practice. There was a significant reduction in unadjusted odds of perinatal mortality among women under the care of midwives beyond the first year compared with those within the first year (OR 0.79, 95% CI 0.67 to 0.93) but no significant reduction in risk remained after adjusting for known risk factors, (OR 0.89, 95% CI 0.74 to 1.07). There was a significant increase in the adjusted odds of perinatal mortality among midwives booking a caseload of 15 or fewer mothers per year (1.34, 1.01 to 1.78) and 16 to 30 (1.25, 1.04 to 1.50) compared with midwives booking 51 to 80. CONCLUSIONS: Findings suggest that the first year of midwifery practice is not associated with an increased risk of perinatal mortality but there is evidence that early career midwives are caring for higher-risk women. These findings suggest inequity of access for higher-risk women to experienced midwives and highlight an opportunity to improve support for vulnerable women and new midwives.