RACIAL DISPARITIES IN FROZEN EMBRYO TRANSFER SUCCESS

Abstract

Racial and ethnic disparities in pregnancy outcomes have been reported after fresh in vitro fertilization (IVF) cycles, but there are limited data on disparities after frozen embryo transfers (FETs). The objective of this study was to compare pregnancy and live birth rates after FETs among women of different self-reported race/ethnicity groups and explore the effect of patient, protocol, and cycle characteristics on success. Retrospective cohort study Women undergoing an autologous FET between January 2013 and March 2020 were included. Co-maternity, surrogacy, donor oocyte/embryo cycles, or those not surviving the thaw were excluded. Demographics and clinical characteristics including self-reported race and ethnicity were abstracted from the medical record. Continuous variables were compared using the Student’s t-test or Mann–Whitney U test while the χ2 or Fisher’s exact tests were used to compare categorical variables. Multivariable logistic regression was used to examine the relationships between pregnancy, live birth, and race while adjusting for potential confounders. White, Black, and Asian women underwent a total of 1664 (73.7%), 257 (11.4%), and 336 (14.9%) frozen embryo cycles, respectively. Only 3.4% of the population self-identified as Hispanic/Latino. Programmed FETs were performed in 83.4% of all cycles (n=1975). Black women were significantly older at the time of egg retrieval, had a higher prevalence of fibroids, higher BMIs, were less likely to transfer PGT-tested blastocysts, and less likely to undergo a single embryo transfer when compared to non-Black women (p < 0.05). Overall, Black women were significantly less likely to achieve pregnancy after FET when adjusting for age, BMI, parity, and number of embryos transferred compared to non-Black women (AOR 0.68, 95% CI 0.51-0.92, p=0.01). Though there was no significant overall difference in live birth rates, endometrial preparation protocol modified the effect of race on live birth. Black women were significantly less likely to achieve a live birth after a natural cycle FET compared to non-Black women (37.1% vs 13.0%, p=0.02), a difference not observed with programmed FETs (42.2% vs 40.0%, p=0.5). A sub-analysis investigating lower implantation rates showed no racial differences in mean estradiol or progesterone within 24 hours of transfer or endometrial morphology in programmed FETs (n=1680). Results were unchanged when restricting the analysis to women without fibroids and non-PGT cycles. In this study using a diverse cohort of more than 2000 women, Black race was associated with a significantly lower rate of embryo implantation following FET independent of the effects of endometrial preparation protocol, PGT, and established predictors of treatment success. Our finding that racial differences in live birth after FET may depend on the endometrial preparation protocol is novel and requires further study. Disparities in success are not only important for patient counseling, but also warrant further investigation to develop strategies to improve success rates in Black women.