Preterm Deliveries in Women with Uterine Myomas: The Japan Environment and Children’s Study

This study aimed to clarify the association between uterine myomas and preterm birth (PTB), preterm premature rupture of membranes (pPROM), and intrauterine infection (II). The study was based on data from the Japan Environment and Children's Study, a nationwide birth-cohort study. Data of 86,370 women with singleton births after 22 weeks of gestation (with uterine myomas, n = 5354) were retrospectively analyzed. Using logistic regression, adjusted odds ratios (aORs) for PTB, pPROM, and II were calculated considering women without uterine myomas as the reference. Additionally, the effects of II on the incidence of PTB and pPROM were evaluated. In women with uterine myomas, the aORs for PTB before 37 and 34 weeks, pPROM, and II were 1.37 (95% confidence interval, 1.22-1.54), 1.61 (1.27-2.05), 1.65 (1.33-2.04), and 1.05 (0.75-1.46), respectively. The aORs for PTB and pPROM in women with II and uterine myomas were not significantly increased. Uterine myomas during pregnancy were associated with an increased incidence of PTB and pPROM. However, II in women with uterine myomas was not associated with an increased incidence of PTB or pPROM. These findings suggest a potential risk of occult PTB in pregnant women with uterine myomas.