Crude and adjusted ORs (with <i>p</i>-value) for all outcomes comparing medical-led to midwife-led care.

<p>Crude and adjusted ORs (with <i>p</i>-value) for all outcomes comparing medical-led to midwife-led care.</p

A Comparison of Midwife-Led and Medical-Led Models of Care and Their Relationship to Adverse Fetal and Neonatal Outcomes: A Retrospective Cohort Study in New Zealand

<div><p>Background</p><p>Internationally, a typical model of maternity care is a medically led system with varying levels of midwifery input. New Zealand has a midwife-led model of care, and there are movements in other countries to adopt such a system. There is a paucity of systemic evaluation that formally investigates safety-related outcomes in relationship to midwife-led care within an entire maternity service. The main objective of this study was to compare major adverse perinatal outcomes between midwife-led and medical-led maternity care in New Zealand.</p><p>Methods and Findings</p><p>This was a population-based retrospective cohort study. Participants were mother/baby pairs for all 244,047 singleton, term deliveries occurring between 1 January 2008 and 31 December 2012 in New Zealand in which no major fetal, neonatal, chromosomal or metabolic abnormality was identified and the mother was first registered with a midwife, obstetrician, or general practitioner as lead maternity carer. Main outcome measures were low Apgar score at five min, intrauterine hypoxia, birth-related asphyxia, neonatal encephalopathy, small for gestational age (as a negative control), and mortality outcomes (perinatal related mortality, stillbirth, and neonatal mortality). Logistic regression models were fitted, with crude and adjusted odds ratios (ORs) generated for each outcome for midwife-led versus medical-led care (based on lead maternity carer at first registration) with 95% confidence intervals. Fully adjusted models included age, ethnicity, deprivation, trimester of registration, parity, smoking, body mass index (BMI), and pre-existing diabetes and/or hypertension in the model. Of the 244,047 pregnancies included in the study, 223,385 (91.5%) were first registered with a midwife lead maternity carer, and 20,662 (8.5%) with a medical lead maternity carer. Adjusted ORs showed that medical-led births were associated with lower odds of an Apgar score of less than seven at 5 min (OR 0.52; 95% confidence interval 0.43–0.64), intrauterine hypoxia (OR 0.79; 0.62–1.02), birth-related asphyxia (OR 0.45; 0.32–0.62), and neonatal encephalopathy (OR 0.61; 0.38–0.97). No association was found between lead carer at first registration and being small for gestational age (SGA), which was included as a negative control (OR 1.00; 0.95–1.05). It was not possible to definitively determine whether one model of care was associated with fewer infant deaths, with ORs for the medical-led model compared with the midwife-led model being 0.80 (0.54–1.19) for perinatal related mortality, 0.86 (0.55–1.34) for stillbirth, and 0.62 (0.25–1.53) for neonatal mortality. Major limitations were related to the use of routine data in which some variables lacked detail; for example, we were unable to differentiate the midwife-led group into those who had received medical input during pregnancy and those who had not.</p><p>Conclusions</p><p>There is an unexplained excess of adverse events in midwife-led deliveries in New Zealand where midwives practice autonomously. The findings are of concern and demonstrate a need for further research that specifically investigates the reasons for the apparent excess of adverse outcomes in mothers with midwife-led care. These findings should be interpreted in the context of New Zealand’s internationally comparable birth outcomes and in the context of research that supports the many benefits of midwife-led care, such as greater patient satisfaction and lower intervention rates.</p></div

Numbers and incidence rates of perinatal outcomes by 1,000 total and live births.

<p>Numbers and incidence rates of perinatal outcomes by 1,000 total and live births.</p

Characteristics of the overall cohort and the midwife-led and medical-led groups.

<p>Characteristics of the overall cohort and the midwife-led and medical-led groups.</p

Adjusted ORs of PRM and birth asphyxia/hypoxia/neonatal encephalopathy in relation to maternal characteristics.

<p>Adjusted ORs of PRM and birth asphyxia/hypoxia/neonatal encephalopathy in relation to maternal characteristics.</p

Adjusted ORs of low Apgar and small for gestational age in relation to maternal characteristics.

<p>Adjusted ORs of low Apgar and small for gestational age in relation to maternal characteristics.</p

Associations between smoking amount and breast cancer incidence by ethnic group.

*<p>adjusted for age, menopause status, age at menarche, BMI, exercise, HRT, OC, maternal breast cancer, parity, alcohol, and SEP.</p

Characteristics of population controls according to never/ever smoking status.

<p>Characteristics of population controls according to never/ever smoking status.</p

Unadjusted and adjusted ratio of geometric means for volumetric absolute mammographic density by ethnicity and age.

<p>Unadjusted and adjusted ratio of geometric means for volumetric absolute mammographic density by ethnicity and age.</p

The effect of adjusting associations between smoking and breast cancer for potential confounders individually.

*<p>ever smoked status, adjusted for age, menopause status, age at menarche, SEP.</p