The Northwestern University triplet study. IV. Biochemical parameters

Umbilical arterial and venous blood gas indices of 11 triplet pregnancies were reviewed. Ten sets of triplets were delivered by cesarean section and one set was delivered vaginally. Mean 1-minute Apgar scores were significantly lower in the group of infants delivered third than in either of the other birth order groups. There were no statistically significant differences when the mean umbilical arterial or venous pH, PCO₂, and base deficit were compared among any one triplet and the other two. Similarly, no significant differences were found when these parameters were compared by birth order in relation to mean 5-minute Apgar scores, mean birth weights, and mean gestational ages at delivery. Birth order did not appear to significantly influence acid-base status, although it may become significant with an increasing time in utero after delivery of the firstborn infant. Further study is necessary to investigate whether there is a critical interval of delivery whereby the infants remaining in utero become acidotic.