Introduction: Pregnancy has special conditions that can affect sleep pattern. About 2/3 of pregnant women have abnormal sleep pattern which can cause disorders during pregnancy and after delivery for the mother and fetus. This study aimed to evaluate the quality and disorders of sleep in the last trimester of pregnancy and women referred to gynecology clinic of Tamin Ejtemaee Hospital of Zahedan city. Materials and Methods: In this cross-sectional study, 400 pregnant women (28-40 of pregnancy) referred to the Tamin Ejtemaee Hospital in the spring and summer of 1395, were selected randomly and studied. Data were collected from demographic questionnaire and Pittsburgh Sleep Quality Index (PSQI) and by the continuous sampling method and were analyzed by using descriptive and inferential statistical tests. Findings: The findings demonstrated that the daily sleep average was 8.7 ± 1.7 hours per week. The highest amount of sleep was among student pregnant women (10 hours) and the lowest amount of sleep was among employee pregnant women (8.3 ± 0.9 hours per day). The percentage of sleep disorders in self-employed and worker mothers was more than mothers which had other jobs but it was not significant. Also, there was no significant difference between the variables of education level, income, weight before pregnancy, mother body mass index, delivery typeand sleep disorders. Besides, a significant relation between sleep disorders of the pregnant mother and birth weight of infant was observed and the percentage of low birth weight in mothers which have sleep disorders in the last 3 months, was higher (p = 0.00). Result: Due to the high prevalence of sleep disorders in pregnant women, the need for sleep hygiene in fertility and safe strategies to improve sleep quality in pregnant women is emphasized.