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Background: A quick look at the existing literature indicates that sleep disturbances during pregnancy could be a risk factor for adverse outcomes. The aim of the study was to assess the prevalence of maternal sleep quality in late pregnancy and the association between preterm births and sleep quality.  
Methods: A prospective study was conducted on 300 eligible singleton pregnant women attending the prenatal care clinics, affiliated with Babol University of Medical Sciences. The data were collected through convenience sampling. The self-report Pittsburgh Sleep Quality Index (PSQI) questionnaire was used to measure the pattern and the quality of sleep in pregnant women.
Results: The prevalence of self-reported poor sleep quality was found to be 77% among the pregnant women in Babol, Iran.  The chi-square test did not show any statistically significant difference in characteristics between pregnant women with good and poor sleep qualities.  Also, the adjusted odds ratio for preterm labor revealed no significant relationships between sleep quality and preterm birth.
Conclusion: The findings demonstrated that there was a high prevalence of poor quality sleep among pregnant women in the third trimester of pregnancy. However, poor sleep quality was not associated with preterm labor, making this problem one of the major problems experienced by pregnant women.