Predictability of Fetal Doppler, Biophysical Profile, and Cardiotocography for Fetal Acidosis at Birth

Fetal Doppler has allowed evaluation of the fetus in both physiological and pathological conditions which has helped in establishing the relationship between Doppler and fetal oxygenation. It is difficult to define pathological acidosis, but the threshold pH of <7 is the best independent predictor for unexplained seizures. Most infants tolerate acidemia well and recover without any remarkable long term sequelae. Worsening umbilical artery acidosis is directly and adversely related to worsening of neurological outcome, hypoxic ischemic encephalopathy, and multiorgan involvement with permanent neurologic injury. Hypoxic ischemic encephalopathy events are not limited to high-risk pregnancies but may occur in about 50 % of the low-risk population. Combination of low pH at birth with other abnormal clinical parameters, e.g., requirement for intubation, 5 min Apgar score ≤5 has 80 % positive predictability of seizures. Predictability of fetal Doppler examination for asphyxiated fetuses is in the tune of 86 %. High-risk pregnancies are screened antenatally by fetal Doppler, biophysical profile, and CTG to identify at-risk fetuses which are confirmed by the ABG analysis of cord blood immediately after birth. All these noninvasive modalities complement each other to identify, at the earliest, any clinical deterioration. Isolated abnormal, e.g., absent end diastolic flow in umbilical artery, abnormal biophysical profile, or nonreactive CTG are not adequately sensitive in identifying these fetuses which was observed in the present cohort. Thus, fetal Doppler in combination with biophysical profile supplemented with cardiotocograph helps in identifying at-risk fetuses for fetal acidosis and encephalopathy and helps in considering early intervention.