Effect of pre-gravid body mass index on outcomes of pregnancies following in vitro fertilization

Purpose To examine the effect of pre-gravid body mass index (BMI) on perinatal outcomes in in vitro fertilization (IVF) singleton pregnancies. Methods Retrospective population-based cohort study. All singleton pregnancies delivered at >= 22 weeks' in Slovenia between 2002 and 2015 were included. Logistic regression analysis was used to examine the relationship between BMI category and outcomes, controlling for potential confounding variables. Interaction term was included to evaluate whether effects of obesity on perinatal outcomes differ in IVF vs. non-IVF pregnancies. We counted the frequencies of hypertensive disorders of pregnancy, gestational diabetes, cesarean delivery, preterm births, and small as well as large for gestational age neonates, neonatal respiratory distress syndrome, neonatal intraventricular hemorrhage, and perinatal deaths. Results Pre-gravid overweight and obesity were associated with higher rates of hypertensive disorders, gestational diabetes, and cesarean deliveries in both IVF and non-IVF pregnancies. Pre-gravid underweight was associated with small for gestational age neonates in IVF and non-IVF pregnancies. There was a significantly lower effect of pre-gravid obesity on the incidence of hypertensive disorders (odds ratio (OR) 0.7; 95% confidence interval (CI) 0.5-0.9) and cesarean delivery (OR 0.8; 95% CI 0.7-0.99) in IVF vs. non-IVF pregnancies. The effect of pre-gravid obesity on neonatal mortality was significantly greater in IVF compared to non-IVF pregnancies (OR 4.6; 95% CI 1.4-15.8). Conclusions Pre-gravid BMI has an important effect on perinatal outcomes in pregnancies following IVF.