Low Apgar score without acidosis may indicate neuromuscular disorder

We hypothesized that in term infants low Apgar score with normal umbilical artery pH (UApH) indicates prenatal damage to the neuromuscular system.

Retrospective database search of 42,117 liveborn infants born 1993-2005. Medical record analysis of 3104 term infants with cardiorespiratory maladaptation referred for special neonatal care. Focus on infants with UApH >7.00 and 5-min Apgar <6 (group A, n=74), UApH <7.00 and 5-min Apgar >5 (group B, n=49), and UApH <7.00 and 5-min Apgar <6 (group C, n=14).

Incidence of 5-min Apgar score <6 was 0.50% in term infants. Mean (SD) UApH was 7.262 (0.075, P=0.075); incidence of UApH <7.00 was 0.30% in term infants. Nucleated red blood cells were elevated without differences in all three groups. Parental consanguinity was present in 39 of the 137 maladapted infants. In groups A/B/C, 10/18/2 infants were small for gestational age (P=0.002 for A vs B) and in 16/1/0 neuromuscular anomalies were identified (P=0.004 for A vs B). Eight of the 17 anomalies had been suspected prenatally. Logistic regression proved neuromuscular disorder the only independent variable discriminating between groups A and B.

Neuromuscular problems are the cause rather than the result of maladaptation. For unexplained low Apgar score, especially without acidosis, meticulous examination of the infant including brain imaging and EEG is justified.