The impact of obesity on outcomes of midwife-led pregnancy and childbirth in a primary care population: a prospective cohort study

ObjectiveTo assess the impact of obesity on the likelihood of remaining in midwife-led care throughout pregnancy and childbirth. DesignSecondary analysis of data from a prospective cohort study. SettingDutch midwife-led practices. PopulationA cohort of 1369 women eligible for midwife-led care after their first antenatal visit. MethodsFirst-trimester body mass index (BMI) was calculated as weight measured at booking divided by height squared. Obstetric data were retrieved from medical records. Multiple logistic regressions were performed to examine the effects of BMI classification on midwife-led pregnancies and childbirths. Main outcome measuresPercentages of women remaining in midwife-led care throughout pregnancy and throughout childbirth. ResultsOf women in obesity classes II and III, 55% remained in midwife-led care throughout pregnancy and 30% remained in midwife-led care throughout birth. Compared with women of normal weight, women in obesity classes II and III had fewer midwife-led pregnancies (OR 0.38, 95%CI 0.21-0.69), and women who were overweight or in obesity classI had fewer midwife-led childbirths (OR 0.63, 95% CI 0.44-0.90; OR 0.49, 95% CI 0.29-0.84, respectively). Compared with women of normal weight, women who were obese had higher referral rates for hypertensive disorders (4 versus 14%), prolonged labour (4.6 versus 10.4%), and intrapartum pain relief (4 versus 10.4%). The women who were eligible for midwife-led birth and who were overweight or obese, had no more urgent referrals than women of normal weight. Women who were obese and who completed a midwife-led birth had no more adverse outcomes than women of normal weight, with the exception of higher rates of large for gestational age (LGA) babies (>97.7 centile; 12.1%, versus 1.9% in normal weight and versus 3.3% in overweight women). ConclusionsAlthough fewer women who were obese remain in midwife-led care during pregnancy and childbirth, there was no increased risk of unfavourable birth outcomes for women who were obese and eligible for a midwife-led birth when compared with women of normal weight. This indicates that when primary care midwives use a risk assessment tool throughout pregnancy and childbirth they are able to safely assign women who are obese to either midwife-led or obstetrician-led care.