Placental histopathology in IVF pregnancies resulting from the transfer of frozen-thawed embryos compared with fresh embryos

Purpose To study whether placentas of singleton pregnancies conceived after fresh embryo transfer (ET) contain more histopathological lesions compared with placentas of singleton pregnancies conceived after frozen-thawed embryo transfer (FET). Methods A prospective cohort study of placental histopathology in 131 women with singleton IVF pregnancies who delivered at a single medical center, between December 2017 and May 2019. The prevalence of different placental histopathology lesions was compared between women who conceived after fresh ET and FET. Results Women who conceived after fresh ET ( n = 74) did not differ from women who conceived after FET ( n = 57) with regard to maternal age, BMI, nulliparity, or infertility diagnosis. Gestational week at delivery was lower in pregnancies conceived after fresh ET (38.5 vs. 39.2 weeks, respectively, p = 0.04), and a trend for a lower birthweight following fresh ET was noted (3040 vs. 3216 g, respectively, p = 0.053). However, placental histopathology analysis from pregnancies conceived after fresh ET was comparable to pregnancies conceived after FET, with regard to the prevalence of maternal vascular malperfusion lesions (45.9% vs. 50.9%, respectively, p = 0.57), fetal vascular malperfusion lesions (17.6% vs. 21.1, p = 0.61), acute inflammatory response lesions (28.4% vs. 28.1%, respectively, p = 0.96), and chronic inflammatory response lesions (13.5% vs. 8.8%, respectively, p = 0.48). Conclusion Placental histopathology did not differ between IVF pregnancies conceived after fresh and frozen ET. These results are reassuring for clinicians and patients who wish to pursue with transferring fresh embryos.