Risk factors for non-previa placenta accreta spectrum in pregnancies conceived through frozen embryo transfer during a hormone replacement cycle in Japan.

Purpose: Non-previa placenta accreta spectrum (PAS) is associated with assisted reproductive technology (ART), particularly frozen embryo transfer during hormone replacement therapy (HRC-FET). We especially aimed to evaluate the prevalence and risk factors for non-previa PAS in HRC-FET pregnancies.

Methods: Overall, 279 women who conceived through ART at three ART facilities and delivered at a single center were included in this retrospective study. Data regarding endometrial thickness at embryo transfer, previous histories, and type of embryo transfer-HRC-FET, frozen embryo transfer during a natural ovulatory cycle (NC-FET), and fresh embryo transfer (Fresh-ET)-were collected. Univariable logistic regression analyses were conducted.

Results: The prevalence of non-previa PAS was 27/192 (14.1%) in the HRC-FET group and 0 (0.0%) in both the NC-FET and Fresh-ET groups. Significantly high odds ratio [95% confidence interval] of non-previa PAS was associated with a history of artificial abortion (6.45 [1.98-21.02]), endometrial thickness <8.0 mm (6.11 [1.06-35.12]), resolved low-lying placenta (5.73 [2.13-15.41]), multiparity (2.90 [1.26-6.69]), polycystic ovarian syndrome (2.62 [1.02-6.71]), and subchorionic hematoma (2.49 [1.03-6.04]).

Conclusions: A history of artificial abortion, endometrial thickness <8.0 mm, and resolved low-lying placenta may help in antenatal detection of a high-risk population of non-previa PAS in HRC-FET pregnancies.