Reliability of antenatal testing: estriol levels versus nonstress testing.

During the third trimester of pregnancy, 334 high-risk patients were followed with antenatal fetal heart rate (FHR) evaluation and with serial determinations of unconjugated plasma estriol. The antenatal FHR tests included nonstress testing (NST) and investigation of beat-to-beat variability. Data indicate that the NST was more reliable than estriol analysis in assessing fetal compromise. While predictive values of negative test results did not differ statistically, the NST/beat-to-beat assessment was particularly accurate in identifying fetal jeopardy in more than 45.0% of the fetuses at risk, whereas only 22.8% cases of jeopardy were accurately predicted by abnormal estriol values. An abnormal NST with loss of beat-to-beat FHR variability should therefore take precedence over plasma estriol determinations during antenatal surveillance of high-risk obstetric patients.