In vitro fertilization and adverse pregnancy outcomes in the elective single embryo transfer era

Objective: To estimate the association between in vitro fertilization (IVF) pregnancy and adverse pregnancy outcomes during delivery hospital admission in a contemporary, nationwide cohort of births in the United States. Study Design: This retrospective, population-based cohort study used the National Inpatient Sample database to identify patients discharged from hospital following delivery from 2014-2019. IVF pregnancies were identified using International Classification of Disease-9/10 codes. Crude and adjusted odds ratios of preterm birth and other clinically significant adverse pregnancy outcomes were evaluated using multivariable logistic regression models. Trends in preterm birth and multiple pregnancy were estimated over the study period. The contribution of multiple pregnancy to preterm birth in IVF pregnancy was estimated in a mediation analysis. Results: IVF-pregnancy delivery discharges were associated with 3.25 times the odds of preterm birth (95% CI 3.05-3.46, p<0.001) compared to non-IVF pregnancy deliveries. Odds of preterm birth in IVF pregnancy delivery discharges decreased over the study period (p-value for linear trend=0.009). The proportion of multiple pregnancies decreased in IVF pregnancy delivery discharges but remained stable in non-IVF pregnancy deliveries. The proportion of the adjusted effect of IVF pregnancy on preterm birth mediated through multiple pregnancy was 67.6% (95% CI 62.6–72.7%). Conclusion: While the odds of adverse pregnancy outcomes is increased compared to non-IVF pregnancies, the odds of preterm birth and multiple gestation have decreased among IVF pregnancies in the United States.