Umbilical cord cortisol in breech delivery

Mixed umbilical cord blood samples were obtained in 31 cases immediately after vaginal breech delivery at term and in 31 cases immediately after vaginal vertex delivery at term. The total cortisol concentrations were determined using a direct radioimmunologic method (Amerlex cortisol kit). The mean umbilical cord total cortisol concentration was 790 +/- 363 nmol/liter in breech delivery as compared with 493 +/- 125 nmol/liter in vertex delivery. The difference was highly significant (p less than 0.0005). There was a highly positive correlation (r = 0.59, p less than 0.0005) between duration of labor and total cortisol concentrations in umbilical plasma after breech delivery. In contrast to that we found only a slightly positive correlation between duration of labor and total cortisol concentrations after vaginal vertex delivery (r = 0.23, p less than 0.10). Significant differences in pH values between breech and vertex deliveries (p less than 0.01) and a slight but significant correlation (r = 0.35, p less than 0.002) between umbilical vein pH values and umbilical total cortisol concentrations indicate that the increase in cortisol during vaginal breech delivery could be attributed partially to some hypoxic events. These results support the concept that the increase in cortisol in the umbilical cord plasma during labor reflects the fetal adrenal response secondary to stress in utero and contribute to our understanding of why an increased risk exists for the fetus during vaginal breech delivery of long duration.