Women's sleep quality has been reported to change during pregnancy; prevalence estimates of poor sleep quality during pregnancy vary widely. To further understand the observed variation of findings, we conducted a meta-analysis to quantify the prevalence of poor sleep quality during pregnancy. Articles (N = 24) that reported prevalence of poor sleep quality as captured by the Pittsburgh sleep quality index (PSQI) ≥ 5 were included, with a total of 11,002 participants contributing data. PubMed, PsycINFO, and Web of Science databases were systematically searched. Results indicated that the average PSQI score during pregnancy was 6.07, 95% confidence interval (CI) [5.30, 6.85], and 45.7%, 95% CI [36.5%, 55.2%], of pregnant women experienced poor sleep quality. Longitudinal studies indicated that sleep quality decreased from second (M = 5.31, SE = 0.40) to third trimester (M = 7.03, SE = 0.85) by 1.68 points, 95% CI [0.42, 2.94]. Gestational age moderated the average PSQI scores and prevalence of PSQI scores ≥5; older samples reported higher mean PSQI scores and higher prevalence of poor sleep quality. Clinicians should be aware that some reduction in sleep quality is expected during pregnancy, but complaints of very poor sleep quality could require intervention. Future research should examine various factors underlying poor sleep quality during pregnancy.