Association between apgar score at 5 minutes and adverse outcomes among Low-Risk pregnancies

Among low-risk pregnancies, we aimed to ascertain the association between 5-minute Apgar score and adverse outcomes of newborn-maternal dyad.We conducted a retrospective cohort study using the U.S. vital statistics datasets (2012-2016), including live births from low-risk women with non-anomalous singleton gestations who delivered at 37-41 weeks. Apgar score was categorized as low (0-3), moderate (4-6), and normal (7-10). The primary outcome was composite neonatal adverse outcome (any of the following: assisted ventilation > 6 h, neonatal seizure, or neonatal death). The secondary outcomes were infant mortality and composite maternal adverse outcome (any of the following: admission to the intensive care unit, blood transfusion, uterine rupture, or unplanned hysterectomy). Multivariable Poisson regression analyses were used to estimate the association between 5-minute Apgar score and adverse outcomes (using adjusted relative risk [aRR] and 95% confidence intervals [CI]).Of 19.9 million live births delivered between 2012 and 2016, 11.7 million (58.7%) met inclusion criteria; 98.9% had a normal 5-minute Apgar score, 0.9% had a moderate score, and 0.2% had a low score. The overall composite neonatal adverse outcome was 3.2 per 1,000 live births and the rates were significantly higher among those with a moderate (aRR 20.8; 95% CI 20.2-21.4) or low score (aRR 43.1; 95% CI 41.6-44.5) than normal score. The overall composite maternal adverse outcome was 2.45 per 1,000 live births and it was significantly higher in deliveries with a moderate (aRR 3.1; 95% CI 2.9-3.3) and low (aRR 4.6; 95% CI 4.2-5.0) 5-minute Apgar score than those with a normal score. Infant mortality also showed a similar pattern.Though approximate 1% of live births had a 5-minute Apgar score below 7 among low-risk pregnancies, a decreased score was associated with a significantly higher risk of neonatal and maternal adverse outcomes, as well as infant mortality.