A retrospective cohort study of the association between midwifery experience and perinatal mortality

Abstract

Objective To determine whether experience of midwife-only and nurse-midwife lead maternity carers (LMCs) is related to perinatal mortality. Methods In a retrospective analysis, routinely collected data were obtained for all pregnancies resulting in live births (or stillbirth at > 20 weeks or weighing > 400 g) in New Zealand in 2005-2009. An anonymized dataset of date of midwife registration was used. The main outcome measure was perinatal mortality (fetal deaths and neonatal deaths > 27 days). Results Among 233 215 eligible births, 84 043 were linked to a midwife-only LMC and 150 172 to a nurse-midwife LMC. Among pregnancies with midwife-only LMCs, perinatal mortality was higher when the midwife had less than 1 year of experience than when the midwife had 5-9 years' experience (rate ratio 1.33; 95% confidence interval 1.02-1.73), an absolute difference of two additional deaths per 1000 births. There was a decreasing rate of perinatal mortality with increasing experience (P = 0.031). Perinatal mortality rates did not differ by experience in the nurse-midwife group. Conclusion Pregnancies cared for by early-career (< 1 year) midwife-only LMCs were associated with a 33% increase in perinatal mortality. No association between experience and perinatal mortality was found for nurse-midwives. Midwife-only trained LMCs could require additional training and/or supervision in their first year of practice.