Perinatal outcome with the modified biophysical profile

Our purpose was to evaluate perinatal outcomes in high-risk pregnancies monitored with a modified biophysical profile.

All non-insulin-dependent patients referred for antepartum fetal surveillance received a modified biophysical profile biweekly. A modified biophysical profile is a combination of a nonstress test and an amniotic fluid index. Patients with a singleton gestation and intact membranes were entered into a protocol of randomized backup testing for an abnormal modified biophysical profile. Those patients having a nonreactive fetal heart rate, significant variable decelerations, late decelerations, or an amniotic fluid index < or = 5.0 cm received either a contraction stress test or a biophysical profile immediately. Once randomized, a patient received the same backup test, when indicated, with subsequent testing.

A total of 2774 patients had 17,429 tests with an uncorrected perinatal mortality rate of 2.9 per 1000. The overall incidence of an adverse perinatal outcome (i.e., perinatal death or nursery death before infant hospital discharge, cesarean delivery for fetal distress within the first 2 hours of labor, 5-minute Apgar score < 7, neonatal seizures or grade III or IV central nervous system hemorrhage) was 7.0%. When compared with patients having persistently normal modified biophysical profile, patients requiring a backup test had a significantly greater incidence of adverse perinatal outcome (9.3% vs 4.9%, p < 0.001, odds ratio 2.0, 95% confidence interval 1.5 to 2.7) and small-for-gestational-age infants (5.2% vs 2.4%, p < 0.001, odds ratio 2.2, 95% confidence interval 1.5 to 3.5). No differences in outcomes between patients randomized to a contraction stress test versus a biophysical profile could be identified either overall or in limiting the analysis to outcome after a negative last test. However, patients having contraction stress test as a backup test had a significantly higher rate of intervention for an abnormal test result than did those having a biophysical profile backup test (23.7% vs 16.6%, p < 0.002, odds ratio 1.6, 95% confidence interval 1.2 to 2.1).

The modified biophysical profile is an excellent means of fetal surveillance and identifies a group of patients at increased risk for adverse perinatal outcome and small-for-gestational-age infants. There does not appear to be a significant benefit with the contraction stress test compared with the biophysical profile as a backup test. Further, the contraction stress test is associated with a higher rate of intervention for an abnormal test than is the biophysical profile.