Introduction: The increasing incidence of gestational diabetes in recent years is an important public health problem. Gestational diabetes can generally be defined as glucose intolerance during pregnancy. Body mass index is a measurement that indicates nutritional status at adults. It is defined as the weight of a person in kilograms, divided by the square of the person's height in meters (kg / m2). Purpose: The purpose was to determine how BMI may have influenced gestational diabetes in the existing correlation between elevated BMI in GDM. Methods: The first part of the diploma work used a descriptive method of literature review, where literature was searched using the CINAHL, COBBIS, PubMed, DiKUL, RUL, Google Scholar databases. The causal non-experimental method of the quantitative empirical approach was then used. Data were obtained from the National Perinatal Information System. Results: The results cover data on pregnant women from all 14 Slovenian maternity hospitals. The sample included women who gave birth in the period from 2013 to 2017 inclusive. The study included 100667 women with normal pregnancies. Based on the data obtained, we found that women with a higher body mass index were more likely to be diagnosed with gestational diabetes. Most women regulate gestational diabetes through diet. Women who were over 30 years of age were also more likely to be diagnosed with gestational diabetes. Women who have both a higher body mass index and gestational diabetes have an increased risk of caesarean section than if they only had one of the following. Regarding shoulder dystocia, vacuum / forceps use, and episiotomy, no changes were observed in the group where the woman had both an increased body mass index and gestational diabetes. Discussion and conclusion: In the future, the study of the studied topic should focus on the study of the growth factors of gestational diabetes. Gestational diabetes is more common at pregnant women with higher body mass index but is also affected by age.