Background and aim: Obese women are at an increased risk of various adverse pregnancy outcomes. The aim of our study was to evaluate the impact of obesity on maternal and neonatal outcomes in a tertiary referral center and to compare obstetric outcomes by the level of maternal obesity.Materials and methods: A cohort study included 3247 women with singleton gestations who gave birth at the Department of Obstetrics and Gynecology, Lithuanian University of Health Sciences, in 2010. Pregnancy complications and neonatal outcomes were identified using the hospital Birth Registry database in normal weight (body mass index [BMI] 18.5–24.9 kg/m2, n = 3107) and prepregnancy obese (BMI ≥30 kg/m2, n = 140) women. Pregnancy outcomes were compared according to the level of obesity (BMI 30–34.9 kg/m2, n = 94 and BMI ≥35 kg/m2, n = 46). Results: Obese women were significantly more likely to have gestational hypertension (OR = 8.59; 95% CI, 5.23–14.14; P < 0.0001), preeclampsia (OR = 2.06; 95% CI, 1.14–3.73; P < 0.0001), gestational diabetes (OR = 5.56; 95% CI, 3.66–8.49; P < 0.0001), dystocia (OR = 2.14; 95% CI, 1.36–3.38; P < 0.0001), induced labor (OR = 2.64; 95% CI, 1.83–3.80; P < 0.0001), failed induction of labor (OR = 18.06; 95% CI, 8.85–36.84; P < 0.0001), cesarean delivery (OR = 1.76; 95% CI, 1.25–2.49; P = 0.001), large-for-gestational-age newborns (OR = 3.68; 95% CI, 2.51–5.39; P < 0.0001). Significantly increased risk of gestational diabetes, preeclampsia, dystocia and newborns with Apgar score ≤7 after 5 min was only observed in women with BMI ≥35 kg/m2. Conclusions: Maternal obesity is significantly associated with an increased risk of gestational hypertension, preeclampsia, gestational diabetes, dystocia, labor induction, failed induction of labor, large-for-gestational-age newborns and cesarean delivery.