Significance of the individual components of the Apgar score.

An analysis of the relationship between the individual components of the 1 min Apgar score, and of each of them with the acid-base status of the infant at delivery, is presented. It is based upon data from four groups of cases: Caesarean section (188), vaginal deliveries conducted under lumbar epidural block (54), and vaginal deliveries without epidural block, the mothers having received no narcotics during labour (84) or having received narcotics during the 6 hours before delivery (85). All the scores were found to be very closely related, the score for colour having the weakest links with the remainder. Each of the component scores, widi the exception of that for colour, correlated well with the values for pH, Pco3 and base excess in umbilical artery blood, and depressant drugs given before delivery appeared not markedly to influence the degree of correlation. The most informative set of components in respect of the acid-base state of the infants appeared to be heart rate and muscle tone and reflex irritability. Inclusion of the score for colour reduces the discriminatory value of the total score. A similarly-directed analysis of the 5 min score was found to be unproductive because of the small number of imperfect scores.