The physiological and physical changes in pregnancy affect the sleep-wake cycle. Limited data exist to evaluate the effect of sleep quality and chronotype during pregnancy on adverse pregnancy outcomes. It is hypothesized that there could be a tendency for the evening chronotype and sleep disturbances to lead to the development of preeclampsia and preterm birth. A total of 313 pregnant women were included. Women were divided into three groups: Group A (control - problem-free), Group B (preeclampsia) and Group C (preterm birth). There were significant differences in the mean PSQI score between the groups (A vs C and A vs B) (p < 0.01). Women in the preterm and the preeclampsia groups reported significantly worse sleep quality. There was a significant difference in the mean MEQ scores between groups (A vs C and A vs B) (p < 0.01). The ratio of the evening-types was significantly higher for the preterm and preeclampsia groups (p < 0.01). Multivariate logistic regression analysis revealed that there is a negative association between preeclampsia/preterm birth and MEQ score, positive association between preeclampsia/preterm birth and PSQI score. Chronotype and sleep quality measurements could provide a simple and feasible way in the prediction of adverse pregnancy outcomes.