Impact of maternal body mass index on neonatal outcome

INTRODUCTION: Maternal body mass index has an impact on maternal and fetal pregnancy outcome. An increased maternal BMI is known to be associated with admission of the newborn to a neonatal care unit. The reasons and impact of this admission on fetal outcome, however, are unknown so far. OBJECTIVE: The aim of our study was to investigate the impact of maternal BMI on maternal and fetal pregnancy outcome with special focus on the children admitted to a neonatal care unit. METHODS: A cohort of 2049 non-diabetic mothers giving birth in the Charite university hospital was prospectively studied. The impact of maternal BMI on maternal and fetal outcome parameters was tested using multivariate regression analysis. Outcome of children admitted to a neonatal ward (n = 505) was analysed. RESULTS: Increased maternal BMI was associated with an increased risk for hypertensive complications, peripheral edema, caesarean section, fetal macrosomia and admission of the newborn to a neonatal care unit, whereas decreased BMI was associated with preterm birth and lower birthweight. In the neonatal ward children from obese mothers are characterized by hypoglycaemia. They need less oxygen, and exhibit a shorter stay on the neonatal ward compared to children from normal weight mothers, whereas children from underweight mothers are characterized by lower umbilical blood pH and increased incidence of death corresponding to increased prevalence of preterm birth. CONCLUSION: Pregnancy outcome is worst in babies from mothers with low body mass index as compared to healthy weight mothers with respect to increased incidence of preterm birth, lower birth weight and increased neonate mortality on the neonatal ward. We demonstrate that the increased risk for neonatal admission in children from obese mothers does not necessarily indicate severe fetal impairment.