Purpose: To compare obstetric outcomes between patients with positive and negative Berlin Questionnaire results. Methods: An observational study comparing outcome between these two groups was carried out in seven hospitals, representing seven different regions of Turkey. In each center, pregnant women who were admitted for normal pregnancy follow-up or labor, were consecutively recruited in the study. Each participant completed a sleep apnea questionnaire from the Berlin Questionnaire. This questionnaire tests snoring and daytime sleepiness. Fetal outcome and pregnancy outcome are recorded from patient files. Results: A total of 465 consecutive patients who completed the Berlin Questionnaire were analyzed. Patients with a positive questionnaire had a higher BMI, pre-pregnancy medical disorder rate and cesarean rate (68% vs 51%) than the negative group. Preeclampsia and gestational diabetes were more prevalent in the positive questionnaire group than the negative questionnaire group [19 (28%) vs 18 (5%) for preeclampsia, 8 (12) vs 13 (3%) for gestational diabetes, respectively]. At logistic regression analysis, gravidity, gestational age at birth and a positive questionnaire were independent predictors for preeclampsia. BMI and history of maternal medical disorders were independent predictors of gestational diabetes mellitus. Conclusion: Obstructive sleep apnea may be related to preeclampsia.