Sleep is one of the common problems during pregnancy, the decrease in sleep quality. Decreased sleep quality can cause many problems during pregnancy and after delivery for the mother and fetus. The current study was done to study the sleep quality of first-time pregnant women in the third trimester of pregnancy referring to health centers. In this study, 168 eligible women referring to health centers were studied. Information was collected using the Pittsburgh Sleep Quality Questionnaire (PSQI), personal, midwifery profile form, and continuous sampling method. Then the data were analyzed by SPSS21 statistical software and using analytical and descriptive statistical tests. This research reveals that 89.88% of pregnant women had unfavorable sleep quality and the average quality of sleep in the third trimester was 8.27±2.91. A decrease in physical activity (p=0.003) and an increase in the mother's age (p=0.04) were related to the unfavorable sleep quality. In addition, women with unfavorable sleep quality had more visits to the doctor's office (p=0.002). Waking up at night because of frequent urination and changing the position in bed had the highest values. For pregnant women, sleep disorders have a high prevalence and it is necessary to pay attention to finding and implementing safe solutions to improve the sleep quality of pregnant women.
