The relationship between Apgar score and umbilical arterial blood gas values in newborns.
The data for this report were derived from 61 newborns and their mothers. Of the newborns 45.9 percent had one-minute Apgar scores of less than seven, and 54.1 percent had Apgar scores of seven or greater. The five-minute Apgar score was less than 7 in 6.6 percent of cases. While 23 percent of newborns had pH values of less than 7.20, 77 percent had pH of 7.20 or greater. Only 39.3 percent of the 28 newborns with one-minute Apgar score of less than 7 and 75 percent of the four newborns with five minute Apgar scores of less than 7 had pH values less than 7.20. Of 33 newborns, 9.1 percent who had Apgar scores of seven or more had pH of less than 7.20. We determined the sensitivity of the one minute Apgar score in acidemia to be 78 percent, the specificity to be 63 percent, the positive predictive value as 39 percent, and the negative predictive value as 90 percent. The one minute score is very poor for detecting acidosis when present but is rarely misleading when acidosis is absent. There was a positive correlation between the Apgar score and pH (p < 0.001). The best correlation with umbilical artery pH values was observed with base excess (-BE) values (p < 0.001). Severe acidosis (pH < 7.11) was detected in eight cases. As delta pH increases, pH, pO2 and HCO3 decrease and pCO2 increases. Of 11 infants with delta pH > or = 0.20, 63.6 percent were sick infants and only one (9%) had normal Apgar scores.