#18 : Risk Factors for Placenta Accreta Spectrum in Pregnancies Conceived after Frozen-Thawed Embryo Transfer in a Hormone Replacement Cycle

Abstract

Background and Aims: Assisted reproductive technology (ART), especially frozen–thawed embryo transfer (FET) in a hormone replacement cycle (HRC) is a risk factor for placenta accreta spectrum (PAS). This study aimed to clarify the risk factors for PAS related to the maternal background and ART techniques in pregnancies conceived after FET in an HRC. Method: We performed a case–control study in two tertiary perinatal centers in Japan. Among 14,028 patients who delivered at ≥24 weeks of gestation or were transferred after delivery to two tertiary perinatal centers between 2010 and 2021, 972 conceived with ART and 13,056 conceived without ART. PAS was diagnosed in patients 1) with histopathological findings of placenta increta/percreta, 2) those requiring manual evacuation of the placenta after delivery, or 3) those with retained placental tissue. Among women who conceived after FET in an HRC, 62 with PAS and 340 without PAS were included in this study. Multivariate logistic regression models were used for case–control comparisons, with adjustment for maternal age at delivery, parity, endometriosis or adenomyosis, the number of previous uterine surgeries of cesarean section, myomectomy, endometrial polypectomy or endometrial curettage, placenta previa, the stage of transferred embryos and endometrial thickness at the initiation of progestin administration. Results: PAS was associated with [Formula: see text]2 previous uterine surgeries (adjusted odds ratio [OR], 3.57; 95% confidence interval [CI], 1.60–7.97) and the number of blastocysts transferred (adjusted OR, 2.89; 95% CI, 1.15–7.26). In patients with <2 previous uterine surgeries, PAS was associated with an endometrial thickness of <7.0 mm (adjusted OR, 5.18; 95% CI, 1.10–24.44). Conclusion: A history of multiple previous uterine surgeries, the number of blastocysts transferred and a thin endometrium before ET are risk factors for PAS in pregnancies conceived after FET in an HRC.