Characteristics of ovarian endometrioma during pregnancy

During pregnancy, the ovarian endometrioma generally decreases in size and occasionally ruptures. We evaluated (1) whether and how ovarian-endometrioma size changes from the first trimester to the postdelivery period, and (2) the type of endometrioma more likely to rupture during pregnancy.

During an 18-year period (2000-2018), ultrasound in the first trimester revealed ovarian endometrioma in 149 pregnant women at our tertiary institute. Among these, we subjected 138 endometriomas in 145 patients to expectant management (wait-and-watch approach during pregnancy). We compared the cyst sizes in the first trimester and the postdelivery period, and defined a >1 cm diameter size-change as a significant increase/decrease. We analyzed four patients with rupture and characterized the predictors of rupture.

A comparison of cyst sizes in the first trimester and the postdelivery period revealed that the size of 94 (68%), 37 (27%), and 7 ovaries (5.0%), respectively, decreased, remained unchanged, and increased; in 56 ovaries (40%), apparent cysts were no longer present. Of the 145 patients, four (2.8%) required emergency surgery for cyst rupture. Adhesion to the surroundings, an increase in cyst size, large size (diameter of ≥6 cm), and compression due to the enlarged uterus in late pregnancy were factors clinically related to rupture.

Approximately two-thirds of ovarian endometriomas decreased in size during pregnancy (40% disappeared), 27% remained unchanged, and only 5% increased in size. However, 2.8% of pregnant women with endometrial cysts experienced rupture. We characterized risk factors for rupture; however, clinical application requires further evaluation.