How often is a low 5-min Apgar score in term newborns due to asphyxia?

To evaluate how often low 5-min Apgar scores (AS(5-min)) at term are associated with asphyxia.

A cohort- and case-control study, including all 183 term infants with AS(5-min) below 7 born at Lund University Hospital during 1993-2002, antepartum deaths excluded. The control group included 183 randomly selected term newborns with AS(5-min) 9-10. Cardiotocography (CTG) traces were assessed blinded to group and outcome. Obstetric and pediatric files were reviewed.

After excluding infants with severe malformations, indications of hypoxia were found at the following rates in cases with AS(5-min) below 4 (N = 30), scores 4-6 (N = 143), and controls (N = 182)-abnormal admission CTG: 38%, 8% and 0.6%; abnormal CTG before birth: 88%, 69% and 18%; obstetrical catastrophe: 28%, 6% and 0.6%; interventions for fetal distress: 83%, 48% and 9%; cord artery pH below 7.15: 69%, 54% and 7%; hypoxic ischemic encephalopathy or hypoxic death: 70%, 14% and none. All differences between each case group and controls were statistically significant (p < 0.0001).

In the absence of severe malformations, the vast majority of AS(5-min) below 4, and at least half of scores 4-6 could be attributed to birth asphyxia. Signs of hypoxia usually appeared during labor, but were present at admission in 38% of cases with AS(5-min) below 4.