Mode of conception and pregnancy outcomes at term among low-risk nulliparous patients

Available data suggest that assisted reproductive technology (ART) is associated with adverse perinatal outcomes; however, prior studies have been confounded by multifetal gestations, preterm birth, and patient medical comorbidities. There are limited data on pregnancy outcomes among ART-conceived low-risk singleton pregnancies delivering at term. Thus, we aimed to measure the association between mode of conception and mode of delivery among low-risk nulliparous patients delivering singleton gestations at term.

Secondary analysis of the ARRIVE trial (NCT01990612), a multicenter randomized, controlled, unmasked, parallel-group trial of nulliparous patients delivering at term, March 2014-August 2017. Pregnancies were categorized by mode of conception as either ART or spontaneous. The primary outcome was cesarean delivery. Secondary outcomes included a composite of perinatal death and severe neonatal complications, and select maternal and neonatal adverse outcomes. Bivariate analyses compared baseline characteristics and outcomes by mode of conception. Primary and secondary outcomes were compared using multivariable logistic regression to generate odds ratios (ORs) and 95% confidence intervals (CIs). Sensitivity analyses by type of ART (in vitro fertilization [IVF] vs. ovulation induction [OI] with or without artificial insemination [AI]) and by embryo age were planned.

Of the 6106 participants in the original trial, 6084 met eligibility criteria: 157 (2.6%) conceived with ART and 5927 (97.4%) did not. Among those with ART, 103 (65.6%) underwent IVF and 54 (34.4%) conceived with OI or AI. Patients undergoing ART were noted to have an older age, differing race/ethnicity, lower body mass index (BMI), more likely to be married, employed full-time, privately insured, and less likely to smoke cigarettes. Cesarean occurred more frequently in those with ART than those spontaneously conceived (29.9% vs. 20.2%; OR, 1.69; 95% CI, 1.20-2.40). This remained significant after adjusting for confounders (aOR, 1.68; 95% CI, 1.15-2.45) and was significant in subgroup analysis comparing IVF conception to spontaneous (31.1% vs. 20.2%; aOR, 1.78; 95% CI, 1.12-2.82). Additionally, there was no difference in hypertensive disorders of pregnancy (aOR, 1.65; 95% CI, 1.00-2.73), other maternal morbidities, and adverse perinatal composite (aOR, 0.90; 95% CI, 0.49-1.67).

Nulliparas delivering a singleton fetus at term conceived by ART had an increased rate of cesarean delivery, with no difference in hypertensive disorders or pregnancy or neonatal outcomes.