CESAREAN SECTION BIRTH AS A FETAL STRESS

Abstract

Umbilical artery (UA) blood gas values were analyzed for 31 infants born by cesarean section. The mean values for pH, PCO2, PO2 and BD were 7.23, 56mm Hg, 18mm Hg. and 9.2mEq/l. Values were similar for infants with and without labor or fetal distress. For 10 Infants born by elective repeat cesarean section (ERCS) under spinal anesthesia (Sp An) the mean values were similar to those in 5 infants born by ERCS under general anesthesia. For those born under Sp An, the interval from Sp An to birth varied from 13 to 32 minutes. There was a very strong relationship between length of this interval and severity of the fetal metabolic acidosis. This interval was 24 minutes or longer for 5 of 6 infants with a BD of more than 9.0mEq/l. Fetal metabolic acidosis was unrelated to maternal blood gas values. A transient drop in blood pressure occurred for 7 or 10 mothers following Sp An. The drop was quickly reversed by intravenous ephedrine. Comparison of the present data with known values obtained in early labor by the Saling technique, and with data for in utero values in the fetal monkey suggest that cesarean section birth constitutes a metabolic stress similar to that caused by labor and vaginal birth. Metabolic acidosis probably occurs during normal labor as a result of decreased uterine blood flow. It is plausible that circulatory adjustments due to Sp An, even when hypotension is pharmacologically reversed, may cause a reduction in flow similar to that caused by labor.