The aim of the study was to compare the perinatal outcome between the normal weight, overweight and obese pregnant women who delivered in the third-level center of reference. Moreover, the objective was to analyze the usefulness of predelivery body mass index (BMI) in prediction of preterm delivery, prolonged second stage of labor, instrumental vaginal delivery, cesarean section, fetal macrosomia, dystocia and newborn acidosis. The retrospective study included 2104 patients, divided into three

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... roups, with BMI between 18.5 and 24.9; 25.0 and 29.9; higher than or equal 30.0 kg/m², respectively. The data was assessed from the medical history. The predelivery obesity increases the risk of cesarean section (aOR 1.63), macrosomia (aOR 8.89) and dystocia (aOR 3.40) in comparison to normal weight women. Moreover, the obese females had three times greater risk of having a macrosomic child (aOR 3.57) and 1.5 times greater risk of cesarean section (aOR 1.52) than overweight group. The role of predelivery BMI in the prediction of cesarean delivery (AUC 0.550; sensitivity 0.39; specificity 0.71, p < 0.001, cut-off value 28.7 kg/m²), macrosomia (AUC 0.714; sensitivity 0.66; specificity 0.70; p < 0.001, cut-off value 29.0 kg/m²) and dystocia (AUC 0.658; sensitivity 0.77; specificity 0.53, p < 0.001, cut-off value 27.0 kg/m²) was significant. The predelivery obesity increases the risk of cesarean section, macrosomia and shoulder dystocia and is a useful parameter in the prediction of perinatal outcomes. The establishing cut-off value for predelivery BMI was the lowest in prediction of shoulder dystocia.