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

To determine whether experience of midwife-only and nurse-midwife lead maternity carers (LMCs) is related to perinatal mortality.

In a retrospective analysis, routinely collected data were obtained for all pregnancies resulting in live births (or stillbirth at ≥20weeks or weighing >400g) 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 ≤27days).

Among 233215 eligible births, 84043 were linked to a midwife-only LMC and 150172 to a nurse-midwife LMC. Among pregnancies with midwife-only LMCs, perinatal mortality was higher when the midwife had less than 1year of experience than when the midwife had 5-9years' 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.

Pregnancies cared for by early-career (<1year) 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.