Abstract Objectives: Maternal overweight and obesity constitute the most important factors causing perinatal complications. The purpose of the study was to analyze obstetrical results in overweight/obese pregnant women with gestational diabetes in relation to Institute of Health recommendations concerning gestational weight gain and assessment of the role of prepregnancy BMI in prediction of macrosomia, pregnancy induced hypertension and cesarean deliveries. Material and methods: Retrospective analysis of 209 overweight and obese pregnant women with gestational diabetes divided into 4 subgroups according to The National Institute of Health (USA) recommendations. The following data were included in the analysis: gestational week in which GDM was diagnosed; HbA1c level in the first and third trimester just before delivery; incidence of pregnancy induced hypertension; incidence of cesarean deliveries; incidence of macrosomia. The following data of II, III, IV subgroups were compared to these found in I subgroup which was classified as the control group. Selected obstetric parameters were also compared between subgroups II, III, IV. Results: The selected parameters of subgroups II, III, IV were not significantly different from these of subgroup I. Pregnancy induced hypertension was diagnosed more frequently among subgroup II in comparison to subgroup III. Using ROC curves analysis, the role of pre-pregnancy BMI was found in the prognosis of: birth weight greater than 4300g, pregnancy induced hypertension, cesarean delivery. Conclusions: 1. The application of the National Institute of Health recommendations on gestational weight gain is limited in case of overweight or obese pregnant women with gestational diabetes mellitus. 2. Excessive weight gain during pregnancy according to National Health Institute recommendations may increase the risk of developing pregnancy induced hypertension in comparison to a pregnant women with weight gain less than recommended, but greater than zero. 3. Increased prepregnancy BMI has a role in prediction of birth weight greater than 4300g, pregnancy induced hypertension, cesarean delivery.