Maternal and fetal blood gas values were studied in 90 selected mothers of comparable age, weight, duration of pregnancy and hematocrit values undergoing cesarean section under balanced general anesthesia in four differing clinical situations: elective with and without placental dysfunction, and emergency with and without fetal distress in apparently normal mothers. Pre-induction (Fi O2 0.21) and pre-delivery (Fi O2 0.60) maternal blood gas analysis, along with umbilical cord blood gas analysis were performed in all cases. Apgar scoring was carried out at one minute and three minutes and correlated with the blood gas values. Out of the 90 cases studied, 36 neonates (40%) showed good apgar scores of greater than seven at one minute and three minutes and correlated well with maternal blood gas values which were within normal ranges. Of the remaining 54 cases (60%) with similar mean maternal gas values the neonates showed an apgar score of less than seven in the first minute. The score improved in three minutes in 35 of them (66%), and umbilical cord blood gas values showed a low pH (umbilical vein 7.22 +/- 0.02 units, umbilical arterial 7.21 +/- 0.01 units) but satisfactory pO2 (umbilical vein 39.4 +/- 1.9 torr, umbilical arterial 2.5 +/- 1.3 torr).(ABSTRACT TRUNCATED AT 250 WORDS)