Spontaneous recovery after severe metabolic acidaemia at birth

Twenty-two severely acidaemic babies (mean umbilical artery pH 7.00), born at term but not requiring resuscitation, were matched for gestational age, mode of delivery and birthweight with non-acidaemic infants. Skin-puncture pH, PCO2 and base deficit were measured at 1 h of age in the acidaemic group. Mean respiratory and heart rates at 30 and 60 min in the two groups were not significantly different. The improvement in pH and base deficit in the acidaemic group correlated with PCO2 at 1 h of age but not with respiratory rates, heart rates or birthweight. However, all four small-for-gestational age infants and one other showed a significantly smaller rise in pH (mean 0.09) compared with the others (mean 0.33). This was associated with a smaller fall in PCO2 and no change in base deficit and these babies were not identified by clinical observations at 1 h of age. Thus, clinical observations of respiratory and heart rates over the first hour of life did not distinguish babies born with severe metabolic acidaemia and did not identify babies who were less efficient at compensating for the acidaemia.