[The relationship between low pH in the umbilical cord artery in neonates and later development of cerebral paresis]

Abstract

Routine determination of the pH in umbilical arterial blood immediately after delivery is a commonly employed variable for assessing the risk of subsequent cerebral paresis caused by hypoxia. Opinions differ regarding the lower limit for normal NS-pH (acidosis limit) and this is due mainly to variable conceptions of what a normal delivery is. Lower limits from 7.04 to 7.14 are thus observed if the limit -2 SD is chosen. Even if the limit of 7.04 is chosen, only very few of the infants who are acidotic on delivery subsequently develop cerebral paresis. The most important reason for this is that the prevalence of cerebral paresis developed as a result of hypoxia during delivery is very low and that a low NS-pH value most probably originates from a neonate who recovers without cerebral paresis. Another reason is that the relationship between the pH value and the degree of hypoxia is far from perfect and this holds also true for the relationship between the degree of hypoxia and cerebral paresis. It is therefore concluded that in connection with cerebral paresis, NS-pH does not fulfill the requirements of a diagnostic test. Determination of NS-pH may, on the other hand, be of significance for neonatal treatment as the combination of a low Apgar score and NS-pH is a reasonable predictor for the neonatal morbidity.