OBJECTIVE Our purpose was to determine the newborn complications after respiratory or metabolic acidosis at delivery and to demonstrate the characteristics of an asphyxial insult predictive of these complications. METHODS Fifty-nine term fetuses with metabolic acidosis were matched with 59 fetuses with normal blood gas measures at delivery. Fifty-one fetuses with respiratory acidosis were also examined. A complication score expressed the magnitude of newborn complications during the 10 days after delivery. RESULTS Newborn complications were not increased after respiratory acidosis. Newborn complications after metabolic acidosis increase in frequency and severity with the increasing severity and duration of the metabolic acidosis. Thirty-two of the 59 newborns in the metabolic acidosis group had a high complication score. The index values predictive of high scores were the duration of the metabolic acidosis and the Apgar score at 1 minute. CONCLUSIONS Intrapartum fetal asphyxia with a severe metabolic acidosis accounts for complications in all newborn systems. The probability of a high complication score increases from 14% with favorable index values to 85% with unfavorable index values.