OP08.01: Changes in ultrasound morphology of ovarian endometriotic cysts during pregnancy

To describe changes in ultrasound morphology and size of endometriomas during pregnancy and to estimate how often endometriomas change during pregnancy and when these changes occur. Patients were examined between years 2012-2020. Patients that underwent at least one ultrasound scan at the ultrasound unit during pregnancy, which showed ovarian endometriosis, were eligible for the study. Pregnancies resulting in miscarriage were excluded. The follow-up schedule included monthly scans until delivery or disappearance of the cyst, and two postpartum scans, after 3 and 12 months, respectively. The latest available ultrasound scan before pregnancy was also analysed. Spearman's test and Wilcoxon's signed test were used for statistical analysis of changes in cyst size. Out of 47 pregnancies in 44 patients, endometriomas developed signs of decidualisation in 23 pregnancies (49%) in 22 patients (50%). Median time for decidualisation was 16 weeks of gestation (range 6 – 29). Cysts showed a tendency to decrease in size throughout pregnancy, and disappearance of the cyst during pregnancy occurred in seven pregnancies (15%), while disappearance of the cyst during postpartum control period occurred in seven pregnancies (15%). Majority of endometriomas undergo changes detected at ultrasound during pregnancy. Half of the patients developed signs of decidualisation during pregnancy with a median time of 16 weeks of gestation, and cysts tended to decrease in size.