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Summary. Three groups of women were delivered by caesarean section before labour: for an abnormal fetal heart rate (FHR) trace (21 cases, group 1), or for maternal deterioration in severe pre‐eclampsia without gross fetal heart rate abnormalities (20 cases, group 2), or to avoid mechanical difficulties in labour at term (30 cases, group 3). The mean gestational ages of the first two groups were 32 weeks with a high proportion of infants small‐for‐gestational‐age. In group 1, FHR variation (mean range of pulse intervals) was less than half (20·6 SE 1·2 ms) of the normal value at the same age (44·4 SE 1·5 ms). This was associated with hypoxaemia (mean umbilical artery Po2 of 6 mmHg at delivery), with evidence of compensation shown by an elevated amniotic fluid erythropoietin. The fetuses were hypoglycaemic and had greater umbilical artery blood alanine concentrations, but no large changes in adenine nucleotide or endorphin plasma concentrations. Although there was a minor degree of respiratory acidaemia at birth, there was not significant metabolic acidaemia. The results demonstrate that the reduced variation of ‘suboptimal’ and ‘decelerative’ fetal heart rate records is associated with fetal hypoxaemia and evidence of nutritional deprivation, but not with asphyxia.

1. After decreasing muscle ATP by a 2 min period of intense exercise, we have studied purine metabolism by using high-pressure liquid chromatography. 2. A major increase in hypoxanthine concentration in plasma and urine was found with increases in xanthine and, in plasma, inosine. Erythrocyte hypoxanthine rose with the level in plasma, but there was no corresponding rise in IMP, the first intracellular metabolite of hypoxanthine. No rises in uridine or urate were found in plasma. 3. Plasma adenosine did not rise and fall significantly after exercise, but a small rise and fall in adenine nucleotide concentrations in plasma was found. 4. Running, swimming and games, which tended to be at the weekend, were associated with a rise in hypoxanthine and xanthine excretion; exercise was probably the cause of the higher excretion during the day than at night. Such activities do not produce changes in concentrations of ATP in muscle, although turnover must rise. 5. The results are consistent with widespread purine exchange between tissues and a 'circulating hypoxanthine pool'.