Introduction:The aim of this study was to describe the influence of maternal pregnancy body mass index (BMI) and maternal weight gain during pregnancy on perinatal and neonatal outcomes.Methods: Retrospective analysis of singleton pregnancies > 37 weeks of gestation delivered between 2004 and 2014. Fetal anomalies and intrauterine deaths have been excluded. Results:Our data demonstrate a correlation between prepregnancy BMI and preeclampsia (k* = 0.029, p = 0.024) as well as between the BMI at the time of delivery and maternal hypertension (k* = 0.443, p = 0.046) and preeclampsia (k* = 0.491, p = 0.02). The results also show a significant relation between maternal BMI and the birth mode (k* = 0.052, p = 0.0003) and between BMI and fetal macrosomia (r = 0.009, p = 0.03). The rate of macrosomic newborns was higher both in obese women (r = 0.165, p = 0.016) as well as in underweight women (r = 0.196, p = 0.036). Weight gain during pregnancy seems to play a minor role compared to the pre-pregnancy BMI and the maternal BMI at the time of delivery. Conclusion:Optimal weight gain during pregnancy in relation to maternal pre-pregnancy BMI remains a controversial issue in perinatology and pregnancy management. Overweight and obese women have an increased risk of preeclampsia, hypertension and macrosomia. Underweight women are also at risk of adverse perinatal outcome.