Fetal pH and postnatal adaptation in preterm vaginal deliveries.

The postpartum adaptation to extrauterine life was studied in 39 preterm (less than 37 weeks of gestation) and 13 term vaginally born infants. Fetal scalp pH during delivery was measured in every baby. Acid-base balance was followed with repeated measurements during the first 30 minutes and at 1 and 12 hours post partum. Heart rate and respiration was monitored with a cardiorespirograph (CRG) during the first 30 minutes and at 24 hours of age. The results showed a more extended delay in acid-base regularisation in the group of preterm infants less than 34 weeks of gestation with low fetal scalp pH (less than 7.20). There was no group difference in postnatal acid-base balance and cardiorespiratory adaptation for infants born after 33 weeks of gestation in comparison to term infants. It is suggested that as regards the capacity for postnatal adaptation 34 rather than 37 gestational weeks should be considered the limit of prematurity.