Leiomyomatous uterus and preterm birth: an exposed/unexposed monocentric cohort study

The risk of preterm birth may increase in the presence of uterine leiomyomas during pregnancy. Whether myomectomy abrogates this risk has never been studied.

Our aim was to evaluate the association between the presence of uterine leiomyomas during pregnancy and preterm birth and, if an association exists, to evaluate its persistence in case of a history of myomectomy.

This exposed/unexposed monocentric retrospective cohort study included all women with singleton pregnancies delivering >22 weeks in a tertiary university hospital maternity unit from January 2011 through September 2015. Women with a leiomyomatous uterus were compared to women with no myomas. Women in the leiomyomatous uterus group were women with uterine leiomyoma(s) during pregnancy (≥1 leiomyoma, measuring ≥20 mm or multiple leiomyomas whatever the size) seen on at least 1 obstetric ultrasound without history of myomectomy, or women with a history of myomectomy (removal of ≥1 leiomyoma, measuring ≥20 mm or multiple leiomyomas whatever the size) by hysteroscopy, laparoscopy, or laparotomy with or without persistent leiomyomas. The association between leiomyomatous uterus and preterm birth was assessed through univariate and multivariable logistic regression.

Among the 19,866 women in the cohort, 301 (1.5%) had a leiomyomatous uterus (154 unoperated women and 147 operated women). The rate of premature delivery was 12.0% in the leiomyomatous uterus group and 8.4% in the nonleiomyomatous uterus group. After adjusting for the risk factors for preterm birth, leiomyomatous uterus was significantly associated with preterm birth (adjusted odds ratio, 2.5; 95% confidence interval, 1.7-3.7). This association was significant for unoperated women (adjusted odds ratio, 2.7; 95% confidence interval, 1.6-4.6) as well as operated women (adjusted odds ratio, 2.3; 95% confidence interval, 1.3-3.9) when compared to the nonleiomyomatous uterus group.

Uterine leiomyomas are associated with preterm birth and this association persists after myomectomy.