OC12.04: *Natural changes of endometriomas during pregnancy and after delivery

To assess changes of endometriomas during pregnancy and after delivery using ultrasound. Women with at least one adnexal mass suggestive of endometrioma were examined with ultrasound during pregnancy every month, thereafter at 3-6 and 7-18 months after delivery at the Ultrasound Unit, Department of Obstetrics and Gynecology, Skåne University Hospital, Malmö, Sweden. Women with at least two ultrasound examinations during pregnancy were included. Morphological changes of endometriomas regarding decidualization, changes in size of the endometrioma and the largest solid component during pregnancy and after delivery were assessed. Decidualization of endometrioma was found in 33 of 57 (58%) included women and was detected the first time at gestational age of 17 weeks (median, IQR 15 – 22). In total, 39 (68%) women had endometrioma detected at ultrasound before pregnancy. Compared to the first trimester, the mean diameter of endometriomas decreased after 22+0 weeks of gestational age (p = 0.005) and continued to decrease throughout the remaining pregnancy and 3-6 and 7-18 months postpartum (p < 0.001). The mean diameter of the largest solid component was larger at gestational age of 22+0 – 25+6 weeks (p < 0.05) and 26+0 – 29+6 weeks (p < 0.05), compared to ultrasound examinations performed before gestational age of 22+0 weeks. No signs of decidualization were found at 3-6 months postpartum. Endometriomas undergo changes in size and morphology during pregnancy. The size of endometriomas decreased after gestational age of 22+0 weeks and more than half of the endometriomas underwent decidualization detected at gestational age of 17 weeks. Solid components increased in size during pregnancy after gestational age of 22+0 weeks.