The value of a negative antepartum test: contraction stress test and modified biophysical profile

To examine the outcome of pregnancies in high-risk patients whose last antepartum fetal assessment was a negative contraction stress test (CST) or a negative modified biophysical profile.

Twenty-nine hundred ninety-four women who received modified biophysical profiles were compared with 2450 who had CSTs during the preceding 3 years. Pregnancy outcomes were evaluated in patients whose last test was negative.

Seventeen hundred fifty-three patients had negative modified biophysical profiles as the last test before delivery, and 1337 had negative CSTs as the last test before delivery. Adverse perinatal outcomes included perinatal death or death before nursery discharge, cesarean delivery for fetal distress within the first 2 hours of labor, 5-minute Apgar score less than 7, neonatal seizures, or grade III or grade IV central nervous system hemorrhage. Adverse outcomes occurred in 90 patients (5.1%) whose last test before delivery was a negative modified biophysical profile and in 93 patients (7.0%) whose last test was a negative CST (P = .04, odds ratio 1.38, 95% confidence interval 1.01-1.88). Overall, there were 11 perinatal deaths, nine of which resulted from lethal congenital abnormalities.

In this population, the frequency of adverse perinatal outcome following a negative modified biophysical profile was no greater than that following a negative CST. Further, the incidence of potentially preventable perinatal death following a negative modified biophysical profile or CST was less than one per 1000 tested high-risk pregnancies.