Fetal breathing movements and the nonstress test in high-risk pregnancies

Abstract

Three hundred ninety-eight observations of fetal breathing movements (FBM) and the nonstress test (NST) were made in 223 patients. The presence of FBM was noted in a significantly higher proportion of tests with a reactive NST (88%) than a nonreactive NST (67%). Conversely, a significantly higher proportion of tests were reactive when FBM were present (82.6%) than when FBM were absent (49%). A significant relationship existed between either test and the outcome of pregnancy as judged by the five-minute Apgar score or the incidence of fetal distress in labor. Combining two normal tests did not improve the accuracy in predicting outcome; but the combination of both tests, when abnormal, produced a significant improvement in predicting fetuses likely to have an abnormal outcome. The combination of the normal with the abnormal test had a predictive accuracy similar to a single normal test in predicting a normal five-minute Apgar. This combination was associated with an incidence of fetal distress in labor intermediate between that seen with either the normal or abnormal test when alone. Neither a single test nor the combination of tests as helpful in identifying the small-for-gestational age (SGA) infants. These data indicate antepartum fetal evaluation may be improved when more than one biophysical variable is used.