Umbilical arterial and venous blood samples were obtained at birth immediately after clamping the cord in 38 infants. Simultaneously, maternal arterial samples were collected. Arterial blood samples were analyzed for acid-base blood gas content and venous blood samples were analyzed for plasma ascorbic acid levels. The umbilical plasma ascorbic acid level was significantly higher when compared with maternal plasma levels (172.9 +/- 39.2 vs. 57.8 +/- 21.0 mumol/liter, p < 0.0001). Correlations between maternal ascorbic acid levels and umbilical cord levels proved to be insignificant. Umbilical ascorbic acid levels in the 2 groups of infants characterized by the presence or absence of fetal distress showed significantly higher levels in the fetal distressed group (17 infants) when compared to the non-distressed group (21 infants)--191.9 +/- 36.0 vs. 157.4 +/- 34.6 mumol/liter, p < 0.005. The use of an umbilical cord ascorbic acid cut-off point of 95.8 mumol/liter gave a sensitivity of 76% and a specificity of 67% as predictors for the presence or absence of fetal distress (p < 0.025). The results of the present study demonstrate a substantial increase in ascorbic acid levels in infants exposed to intrapartum fetal distress, without any clinical sign of such insult at or after birth.