IN OVULATORY WOMEN, TRANSFER OF FROZEN EMBRYOS IN THE NATURAL CYCLE IS ASSOCIATED WITH LOWER ODDS OF HYPERTENSIVE DISORDERS OF PREGNANCY

Abstract

The presence of a corpus luteum and its associated synthetic function is increasingly recognized as an important aspect of early placental development. We sought to determine if frozen embryo transfer (FET) in the natural versus the programmed cycle is predictive of hypertensive disorders of pregnancy (HDP) and small for gestational age (SGA) in ovulatory women who have the option for either FET cycle. Retrospective cohort study of ovulatory women with singleton pregnancies who underwent FET in the natural or programmed cycle and had a live birth >20 weeks at a single institution from 2013-2019. The primary outcome was HDP during the delivery hospitalization. The secondary outcome was SGA. We performed multivariable logistic regression analyses to determine if frozen transfer cycle type predicts (1) HDP and (2) SGA, controlling for age, pre-pregnancy BMI, trophectoderm biopsy, maternal comorbidities (diabetes, hypertension, antiphospholipid antibody syndrome, or lupus), and antenatal aspirin use in both regression models. We included 299 women (78.3%) who underwent natural FET and 109 women (26.7%) who underwent programmed FET. Demographic characteristics were similar between groups. The most common type of HDP diagnosed was gestational hypertension (74.7%), followed by pre-eclampsia with severe features (10.5%), and without severe features (8.4%). The adjusted prevalence of SGA was 10.4% in natural FET and 7.4% in programmed FET. When compared to transfer in the natural cycle, transfer in the programmed cycles was associated with higher odds of HDP (aOR: 1.65, 95% CI: 1.01-2.72, p=0.048). The adjusted prevalence rate of HDP was 22.1% in natural FET and 32.4% in programmed FET. Transfer cycle type was not associated with a diagnosis of SGA (aOR: 0.72, 95% CI: 0.32-1.65, p=0.443). In ovulatory women conceiving via FET, transfer in the natural cycle, where a corpus luteum is present, is associated with lower odds of HDP compared to programmed FET cycles. Natural FET cycles may represent an opportunity for risk reduction in a cohort of infertile women already at risk for pregnancy complications.