The association between 5-min Apgar score and mortality disappears after 24 h at the borderline of viability

Abstract

Aim: To quantify the relationship between 5-min Apgar scores and infant mortality for infants at the borderline of viability.

Methods: Cohort study of 7008 infants 23-25 weeks' gestation using 2002 US National Center for Health Statistics data. Using Cox proportional-hazards models, we quantified the relationship between Apgar score and infant mortality for all infants, and then infants surviving their first 24 h. Models were adjusted for gestational age, birth weight, gender, delivery method, plurality, maternal race, marital status and education.

Results: Within one year, 46% of infants died. Of the non-survivors, deaths within 24 h were more common among infants with Apgar scores 0-3 (83%) than among infants with Apgar scores 7-10 (13%). When including all infants and adjusting for potential confounders, each 1-point increase in Apgar score decreased the hazard of mortality by 0.82. However, after excluding infants who died within 24 h, the hazard ratio increased to 0.95; although statistically significant, the practical impact was negated.

Conclusions: For 23-25 week gestation infants surviving the first 24 h, the Apgar score loses clinical significance. Clinicians should be aware of the limitations of clinical assessments in the delivery room.