Effects of obstetric regional analgesia and of asphyxia on the arterial blood concentrations of the lipid metabolites: glycerol, free fatty acids and beta-hydroxybutyrate were investigated in 85 newborn infants divided into a control group, an asphyxia group, a continuous epidural, an intermittent epidural and a paracervical + pudendal block group: lidocaine was the drug used in the analgesia groups. The postnatal changes in lipid metabolites followed three different patterns. After marked increases in glycerol and free fatty acids a steady level was reached after one hour in the control group and not before two hours in the regional analgesia groups. In the asphyxia group, however, a steady level was found already 10 min after birth. Between 30 and 120 min after birth the beta-hydroxybutyrate concentration increased in the control group, decreased in the asphyxia group and did not change in the three regional analgesia groups. The different patterns of lipid metabolites may indicate differences in sympathetic tone and/or in hormonal influences after birth.