BACKGROUND: Sleep quality is essential for pregnant women and affects their self-efficacy. However, the longitudinal dynamics between these constructs, particularly regarding personality traits, are not well understood. This study aimed to examine the relationship between sleep quality and self-efficacy trajectories among pregnant women, as well as the role of maternal personality traits. METHODS: A prospective cohort design was employed, utilizing consecutive sampling. Pregnant women were assessed at four-time points from early pregnancy to 42 days postpartum. Self-efficacy, sleep quality, and personality traits were evaluated using validated scales. Latent profile analysis and parallel process latent growth curve modeling were employed for data analysis. RESULTS: Poorer initial sleep quality negatively predicted initial self-efficacy (β=−0.459, P<0.05) but positively predicted self-efficacy growth rate (β=0.383, P<0.05). Worsening sleep quality over time was associated with lower self-efficacy growth (β=−0.405, P<0.05). These relationships were significant only for women with mild emotional instability, not those with moderate emotional stability. CONCLUSION: Sleep quality and self-efficacy are closely linked among pregnant women, with maternal emotional stability moderating this association. Further research is warranted to elucidate the underlying mechanisms.