Pregnancy-related changes in the size of uterine leiomyomas

To describe the effects of pregnancy on the growth of leiomyomas using sonographic measurements of leiomyomas taken longitudinally during pregnancy.

The study population included asymptomatic gravidas with singleton pregnancies in whom we identified uterine leiomyomas. We included all women whose leiomyomas were measured at least twice during the pregnancy. In a subgroup of women we also compared the size of leiomyomas before and after the index pregnancy. Using real-time sonography, we measured each leiomyoma in 3 axes and averaged the measurements. During subsequent studies we calculated the percent change in the size of each tumor. We assessed complications related to the presence of these tumors.

We evaluated 137 leiomyomas in 72 women (average, 2.3 +/- 1.8 per woman). Each underwent an average of 3.7 +/- 2.1 scans. The average gestational age at the time of first assessment was 14.4 +/- 5.4 weeks. The average diameter of the leiomyomas at the first study was 34.2 +/- 23 mm. On average, there was no significant change in the size of leiomyomas during pregnancy. We found that the size, location and our ability to visualize leiomyomas varied significantly during pregnancy. Four of the 72 women had obstetric complications related to the presence of leiomyomas.

The findings of our longitudinal sonographic assessment of 137 uterine leiomyomas suggest that despite the commonly held belief that they tend to enlarge during the course of pregnancy, this phenomenon is in fact quite rare.