The impact of embryo vitrification on placental histopathology features and perinatal outcome in singleton live births.

STUDY QUESTION: Does embryo vitrification affect placental histopathology pattern and perinatal outcome in singleton live births? SUMMARY ANSWER: Embryo vitrification has a significant effect on the placental histopathology pattern and is associated with a higher prevalence of dysfunctional labor. WHAT IS KNOWN ALREADY: Obstetrical and perinatal outcomes differ between live births resulting from fresh and frozen embryo transfers. The effect of embryo vitrification on the placental histopathology features associated with the development of perinatal complications remains unclear. STUDY DESIGN, SIZE, DURATION: Retrospective cohort study evaluating data of all live births from one academic tertiary hospital resulting from IVF treatment with autologous oocytes during the period from 2009 to 2017. PARTICIPANTS/MATERIALS, SETTING, METHODS: All patients had placentas sent for pathological evaluation irrelevant of maternal or fetal complications status. Placental, obstetric and perinatal outcomes of pregnancies resulting from hormone replacement vitrified embryo transfers were compared with those after fresh embryo transfers. A multivariate analysis was conducted to adjust the results for determinants potentially associated with the development of placental histopathology abnormalities. MAIN RESULTS AND THE ROLE OF CHANCE: A total of 1014 singleton live births were included in the final analysis and were allocated to the group of pregnancies resulting from fresh (n = 660) and hormone replacement frozen (n = 354) embryo transfers. After the adjustment for confounding factors the frozen embryo transfers were found to be significantly associated with chorioamnionitis with maternal (odds ratio (OR) 2.0; 95% CI 1.2-3.3) and fetal response (OR 2.6; 95% CI 1.2-5.7), fetal vascular malperfusion (OR 3.9; 95% CI 1.4-9.2), furcate cord insertion (OR 2.3 95% CI 1.2-5.3), villitis of unknown etiology (OR 2.1; 95% CI 1.1-4.2), intervillous thrombi (OR 2.1; 95% CI 1.3-3.7), subchorionic thrombi (OR 3.4; 95% CI 1.6-7.0), as well as with failure of labor progress (OR 2.5; 95% CI 1.5-4.2). LIMITATIONS, REASONS FOR CAUTION: Since the live births resulted from frozen-thawed embryos included treatment cycles with previously failed embryo transfers, the factors over embryo vitrification may affect implantation and placental histopathology. WIDER IMPLICATIONS OF THE FINDINGS: The study results contribute to the understanding of the perinatal future of fresh and vitrified embryos. Our findings may have an implication for the clinical decision to perform fresh or frozen-thawed embryo transfer. STUDY FUNDING/COMPETING INTEREST(S): Authors have not received any funding to support this study. There are no conflicts of interest to declare. TRIAL REGISTRATION NUMBER: N/A.