Hormone replacement cycles are associated with a higher risk of hypertensive disorders: Retrospective cohort study in singleton and twin pregnancies

Abstract

Objective: To elaborate the associations of different cycle regimens (natural cycle [NC], stimulated cycle [SC], hormone replacement cycle [HRC]) on maternal and neonatal adverse pregnancy outcomes after frozen–thawed embryo transfers (FET). Design: Population-based registry study. Setting: Swiss IVF Registry. Population or Sample: Singleton (n = 4636) and twin (n = 544) live births after NC-FET (n = 776), SC-FET (n = 758) or HRC-FET (n = 3646) registered from 2014 to 2019. Methods: Fifteen pregnancy pathologies were modelled for singleton and twin pregnancies using mixed models adjusted for cycle regimen, delivery, fertilisation technique, chronic anovulation, age of mother and centre. Main outcome measures: Maternal (vaginal bleeding, isolated arterial hypertension and pre-eclampsia) and neonatal (gestational age, birthweight, mode of delivery) adverse pregnancy outcomes. Results: In singleton pregnancies, the incidences of bleeding in first trimester, isolated hypertension and pre-eclampsia were highest in HRC-FET with doubled odds of bleeding in first trimester (adjusted odds ratio [aOR] 2.23; 95% CI 1.33–3.75), isolated hypertension (aOR 2.50; 95% CI 1.02–6.12) and pre-eclampsia (aOR 2.16; 95% CI 1.13–4.12) in HRC-FET vs. NC-FET and with doubled respectively sixfold odds of bleeding (aOR 2.08; 95% CI 1.03–4.21) and pre-eclampsia (6.02; 95% CI 1.38–26.24) in HRC-FET versus SC-FET. In twin pregnancies, the incidence of pre-eclampsia was highest in HRC-FET with numerically higher odds of pre-eclampsia in HRC-FET versus NC-FET and versus SC-FET. Conclusions: Our data implied the highest maternal risks of hypertensive disorders in HRC-FET, therefore clinicians should prefer SC-FET or NC-FET if medically possible.