Pregnancy complicated with ovarian endometrioma is a risk factor for preterm delivery and rupture or infection during pregnancy. This study aimed to clarify the effectiveness and safety of transvaginal aspiration during pregnancy for endometrioma diagnosed in the first trimester.

This retrospective observational study included 8 pregnant women with endometrioma who underwent transvaginal cyst aspiration at 12–14 weeks (aspiration group) between March 2011–March 2018 and 23 pregnant women with endometrioma who refused aspiration during the same period (observation group).

Characteristics of patients were compared in both groups. Safety, feasability and complications of transvaginal cyst aspiration were reported. Complications and obstetrical outcomes were reported and compared in both groups.

The maximum cyst diameter was 8.9±1.5 cm (mean ± standard deviation) in the aspiration group, which was significantly larger than that in the observation group (4.7±0.2 cm). Four preterm deliveries (17.3%) occurred in the observation group and none in the aspiration group. The emergency cesarean section rate during delivery was 14.2% in the aspiration group and 43.7% in the observation group.

The aspiration group tended to have lower rate of preterm deliveries and emergency cesarean sections, suggesting that cyst aspiration could be an effective, minimally invasive, and safe management option for endometrioma during pregnancy.