To determine when rates of short-term neonatal complications increase beyond 37 weeks of gestation. A retrospective cohort study of all term, cephalic, singleton births delivered at an academic medical center between 1976 and 2001. Data were abstracted from a research quality database and verified with chart review when in question. Primary outcomes included neonatal umbilical artery pH (uapH) and base excess (uaBE), as well as the presence of meconium, 5-minute Apgar scores, and admission to the NICU. Multivariate analyses were performed controlling for maternal ethnicity, weight, age, socioeconomic status, and obstetric history. We found that among the 36,241 women who delivered at 37 completed weeks and beyond, the rates of uapH <7.0, uapH <7.10, uaBE ≤10, and uaBE ≤12, and the presence of meconium all increased throughout term gestations (chi-square, P<0.001). These results persisted when controlling for potential confounders in multivariate models. We found that the rates of immediate neonatal morbidity increase with increasing gestational age. Accurate determination of these rates is important in determining at what gestational age the risk of continuing the pregnancy outweighs that of induction of labor.Tabled 1Weeks of Gestation vs Short-Term Neonatal ComplicationsGestational Age (n)uaBE ≤12 (P<0.001)uapH<7.0 (P<0.001)Meconium (P<0.001)37-39 (15,712)0.87%0.77%15.6%40 (10,873)0.89%0.50%25.8%41 (6,336)1.72%1.09%31.9%42 (2,563)2.03%1.43%35.4%≥43 (747)2.68 %1.33 %37.2 % Open table in a new tab