The relationship between fetal biophysical profile and cord pH in patients undergoing cesarean section before the onset of labor.

In a prospective study of 124 patients undergoing cesarean section before the onset of labor, the fetal biophysical profile was found to have a significant relationship with umbilical cord blood pH (artery and vein). Using cord arterial pH less than 7.20 as a standard for the diagnosis of fetal acidosis, the sensitivity, specificity, and positive and negative predictive values of the fetal biophysical profile score were 90, 96, 82, and 98%, respectively. When the combination of nonreactive nonstress test and absent fetal breathing was used as the "abnormal test," the sensitivity, specificity, and positive and negative predictive values were 100, 92, 71, and 100%, respectively. The first manifestations of fetal acidosis are nonreactive nonstress testing and loss of fetal breathing; in advanced acidemia, fetal movements and fetal tone are compromised. A protocol of antepartum fetal evaluation is suggested based upon the individual biophysical components rather than the score alone.