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

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 betweeen 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 was 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.