[Is there a gestational age dependent risk of acidosis?]

Data from 12,481 delivered newborns show that the duration of gestation has an significant influence on the actual blood-gases and the ph-value. Under comparable clinical conditions in the newborns (Apgar score after one minute) one can observe a steadily increasing metabolic acidosis with increasing maturity of the neonate. Mature and vigorous infants (Apgar score 9 and 10) have, according to our data, an actual pH-value below 7,100 in 0.5 to 0.7% and a pH-value below 7,200 in 13 to 16%. An exaggerated fear of acidosis does not seem justified in these vigorous neonates. In small, vaginally delivered premature newborns, pH-values below 7,200 with an incidence of approx. 28% occur not only more often, but are also combined with severe clinical depression (Apgar score 1-4). Therefore pH-values below 7,200 should be avoided especially in extremely immature neonates. In summary, one observes with increasing immaturity a sort of dissociation of the clinical and biochemical status of the newborn. This observation confirms the efficiency of pH-measurement in umbilical blood. Therefore the definition of the risk of acidosis (number [%] of infants with pH-values below 7,100 [umbilical artery]) should never be analysed alone, but always in combination with the gestational age. Similarly, this statement seems to be valid also for acid-base-values like base-excess, pCO2 and the percentage of oxygen saturation of hemoglobin.