Smaller fetal size in singletons after infertility therapies: the influence of technology and the underlying infertility

ObjectiveTo determine whether fetal size differences exist between matched fertile and infertile women and among women with infertility achieving pregnancy through various treatment modalities.DesignRetrospective cohort study with propensity score analysis.SettingTertiary care center and affiliated community hospitals.Patient(s)1,246 fertile and 461 infertile healthy women with singleton livebirths over a 10-year period.Intervention(s)Infertile women conceiving without medical assistance, with ovulation induction, or with in vitro fertilization.Main Outcome Measure(s)Birthweight; secondary outcomes included crown-rump length, second-trimester estimated fetal weight, and incidence of low birth weight and preterm delivery.Result(s)Compared with matched fertile women, infertile women had smaller neonates at birth (3,375 ± 21 vs. 3,231 ± 21 g) and more low-birth-weight infants (relative risk = 1.68, 95% confidence interval, 1.06, 2.67). Neonates conceived via ovulation induction were the smallest among the infertility subgroups compared with the neonates of fertile women (3,092 ± 46 vs. 3,397 ± 44 g). First-trimester fetal size was smaller in infertile versus fertile women (crown-rump length 7.9 ± 0.1 vs. 8.5 ± 0.1 mm). Within the infertility subgroups, no differences in fetal or neonatal size were found.Conclusion(s)The inherent pathologic processes associated with infertility may have a larger impact on fetal growth than infertility therapies.