Absolute Risk of Adverse Obstetric Outcomes Among Twin Pregnancies After In Vitro Fertilization by Maternal Age

Abstract

Importance: Twin pregnancy is a common occurrence in pregnancies conceived with in vitro fertilization (IVF), but the absolute risk of adverse obstetric outcomes stratified by IVF, twin or singleton pregnancy, and maternal age are unknown.

Objective: To estimate the absolute risk of adverse obstetric outcomes at each maternal age among twin pregnancies conceived with IVF.

Design, setting, and participants: This retrospective cohort study included pregnant women with infants born from January 1, 2013, to December 31, 2018, based on the Hospital Quality Monitoring System in China. Data were analyzed from September 1, 2020, to June 30, 2021.

Exposures: Twin pregnancy with IVF (IVF-T), singleton pregnancy with IVF (IVF-S), twin pregnancy with non-IVF (nIVF-T), and singleton pregnancy with non-IVF (nIVF-S).

Main outcomes and measures: Sixteen obstetric outcomes, including 10 maternal complications (gestational hypertension, eclampsia and preeclampsia, gestational diabetes, placenta previa, placental abruption, placenta accreta, preterm birth, dystocia, cesarean delivery, and postpartum hemorrhage) and 6 neonatal complications (fetal growth restriction, low birth weight, very low birth weight, macrosomia, malformation, and stillbirth).

Results: Among 16 879 728 pregnant women aged 20 to 49 years (mean [SD] age, 29.2 [4.7] years), the twin-pregnancy rates were 32.1% in the IVF group and 1.5% in the non-IVF group (relative risk, 20.8; 95% CI, 20.6-20.9). The most common adverse obstetric outcomes after pregnancy conceived with IVF were cesarean delivery (88.8%), low birth weight (43.8%), preterm birth (39.6%), gestational diabetes (20.5%), gestational hypertension and preeclampsia and eclampsia (17.5%), dystocia (16.8%), and postpartum hemorrhage (11.9%). The absolute risk of most adverse obstetric outcomes in each subgroup presented in 2 dominant patterns: Pattern A indicated the absolute risk ranging from IVF-T to nIVF-T to IVF-S to nIVF-S, and pattern B indicated the absolute risk ranging from IVF-T to IVF-S to nIVF-T to nIVF-S. Both patterns showed an elevated obstetric risk with increasing maternal age in each subgroup.

Conclusions and relevance: In this cohort study, twin pregnancy, IVF, and advanced maternal age were independently associated with adverse obstetric outcomes. Given these findings, promotion of the elective single embryo transfer strategy is needed to reduce multiple pregnancies following IVF technologies. Unnecessary cesarean delivery shouldh be avoided in all pregnant women.

Figure 1.. Flowchart of Data According to Eligibility for Inclusion in This Study

HQMS indicates Hospital Quality Monitoring System; IVF, in vitro fertilization.

Figure 2.. Estimated Absolute Risks of Obstetric Outcomes at Each Maternal Age in Each Subgroup

Data are stratified by in vitro fertilization with singleton pregnancy (IVF-S), IVF with twin pregnancy (IVF-T), non-IVF with singleton pregnancy (nIVF-S), and non-IVF with twin pregnancy (nIVF-T). Data are from China, 2013 to 2018. Estimated absolute risks were calculated by using model 3, with singleton pregnancy and twin pregnancy data for risk by maternal age, with adjustment for geographic region, maternal age, year, ethnicity, and maternal chronic diseases. More images can be seen in the eFigure in the Supplement. Detailed data can be seen in eTable 9 in the Supplement. Dashed lines indicate 95% CIs.