High dosage of gonadotropins is associated with increased risk of preterm birth in singletons born after fresh embryo transfer

Abstract Research Question: Does high gonadotropin dosage affect perinatal outcomes of preterm birth (PTB) and low birth weight (LBW) in singletons born after fresh embryo transfer (ET) cycles? Design: This retrospective cohort study included 12997 singleton births after fresh ET cycles in China from January2013 to December 2020. All women underwent their first IVF/ICSI cycle. Patients were categorized into three groups according to the tertile of total gonadotropin dosage (≤1500 IU, 1501–2100 IU, >2100 IU). Adjusted logistic regression models were performed to calculate odds ratios (ORs) and 95% confidence intervals (CI) for the associations between gonadotropin dosage and the incidence of PTB and LBW. Results: The incidence of PTB and LBW were 6.1% (796/12997) and 4.0% (524/12997), respectively. The incidence of PTB rose from 5.2% (Gn≤1500 IU) to 7.4% (Gn>2100 IU). Compared with the lowest dosage group (≤1500 IU), an elevated incidence of PTB was observed at the highest gonadotropin dosage group (>2100 IU) in adjusted logistic regression model (adjusted OR [aOR]=1.14 [95% CI: 1.04–1.54]). However, the risk of LBW was comparable in three groups. Conclusion: High gonadotropindosage was significantly associated with the increase of PTB risk in singletons born after fresh embryo transfer. Whether mild stimulation regimens using lower dose of gonadotropin could improve pregnancy outcomes needs to be verified in the future studies.