This study was performed to evaluate the relationship between obstructive sleep apnea syndrome and pregnancy complications. A total of 500 women (18-45 years) who had delivered (vaginal delivery or caesarean section) between January 2017 and March 2017 in our clinic were included in the study. Patients at high risk for obstructive sleep apnea syndrome were identified using the Stop Bang questionnaire. Based on the results of the questionnaire, pregnancy complications were compared between high-risk pregnant women (Group 1) and low-risk pregnant women (Group 2). Age, body mass index, smoking rate, and the rate of systemic disease (e.g., diabetes and/or hypertension) were higher in Group 1 than in Group 2 (p < 0.05). Rates of preeclampsia, gestational diabetes, preterm labor, premature rupture of the membranes, and cesarean section were significantly higher in Group 1 than in Group 2 (p < 0.05). Obstructive sleep apnea syndrome is associated with a higher rate of maternal complications among pregnant women. Affected patients should be carefully monitored.