Objective: To investigate the actual sleep conditions at four time points from the last trimester of pregnancy to 3 months postpartum, and to examine the relationship between sleep and minor problems affecting sleep. Methods: A cross-sectional survey on the frequency of minor problems, Pittsburgh Sleep Quality Index (PSQI), and observations in a sleep diary was carried out on women at the end of pregnancy, 2 weeks postpartum, 1 month postpartum, and 3 months postpartum. The questionnaires were distributed to 165 participants. Correlation coefficients were obtained for each item and each scale, and the associations were analyzed. Results: The number of valid responses was 127. In the evaluation of sleep, sleep duration was the shortest and sleep quality was the lowest in the first month after delivery based on the PSQI score. In the correlation between “psychiatric symptoms” and sleep, women with anxiety and nervousness at the end of pregnancy were associated with poorer sleep quality. At all time-points, there was a significant association between “psychiatric symptoms” and poor sleep quality. Conclusion: An association exists between “psychiatric symptoms” and poor sleep quality in women from the last trimester of pregnancy to 3 months postpartum.