EP21.02: Location of the gestational sac in pregnancies conceived by assisted reproductive technology

Previous studies indicate increased risk of placenta previa in pregnancies following blastocyst transfer compared to pregnancies conceived without medical assistance. In this study, we investigated location of the gestational sac in early pregnancies conceived by embryo transfer of fresh or frozen thawed blastocysts. This observational study was performed at St. Olav's Hospital, Trondheim University Hospital, from February 2022 to January 2024. 127 women with an ongoing and normally sited pregnancy after assisted reproductive technology were examined by ultrasound 21 days after single blastocyst transfer, corresponding with gestational week (GW) 5+5. Location of the gestational sac was determined by 3D ultrasound. The uterine cavity was divided into three equal sized parts from fundus to inner cervical os, and location classified as to where 50% of the gestational sac was placed. In GW 5+5, 78 (61%) of the 127 gestational sacs were placed in the upper third, 47 (37%) in the mid third and 2 (1.6%) in the lower third of the uterine cavity. Subgroup analyses comparing 22 fresh and 105 frozen thawed embryos showed no difference in location of the gestational sacs (p 0.31). The absolute majority (98.5%) of the gestational sacs were implanted in the mid or upper third of the uterine cavity. We did not find any difference in location for gestational sacs when comparing fresh versus frozen thawed embryos. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.