Manning and colleagues (1980) proposed the combined use of ive fetal biophysical variables as a more accurate means of assessing fetal health than a single element. Typically, these tests require 30 to 60 minutes of examiner time. Shown in
Table 1i7-2 are the ive fetal biophysical components assessed: (1) heart rate acceleration, (2) breathing, (3) movements, (4) tone, and (5) amnionic luid volume. Normal variables were assigned a score of 2 each, and abnormal variables were given a score of O. Thus, the highest score possible for a normal fetus is 10. Maternal medications such as narcotics and sedatives can signiicantly lower the score (Kopecky, 2000). Ozkaya and associates (2012) found that biophysical test scores were higher if a test was performed in late evening-20:00 to 22:00 hours-compared with 08:00 to 10:00 hours.
TABLE 17-2. Components and Scores for the Biophysical Profile
Nonstress testa :2 accelerations of : 15 beats/min for : 15 sec within 20-40 min Fetal breathing : 1 episode of rhythmic breathing lasting ::30 sec within 30 min Fetal movement ::3 discrete body or limb movements within 30 min Fetal tone ::1 episode of extremity extension and subsequent retun to fiexion Amnionic fluid A pocket of amnionic fluid that measures at least 2 cm in two volumeb planes perpendicular to each other (2 x 2 cm pocket) o or 1 acceleration within 20-40 min <30 sec of breathing within 30 min <3 discrete movements o extension/flexion events Largest single vertical pocket :;2 cm aMay be omitted if all four sonographic components are normal.
bFurther evaluation warranted, regardless of biophysical composite score, if largest vertical amnionic fluid pocket :;2 cm.
Manning and colleagues (1987) tested more than 19,000 pregnancies using the biophysical profile interpretation and management shown in Table 17-3. More than 97 percent of the pregnancies tested had normal test results. They reported a false-normal test rate-defined by an antepartum death of a structurally normal fetus-of approximately 1 per 1000. he most common identiiable causes of fetal death after a normal biophysical profile include fetomaternal hemorrhage, umbilical cord accidents, and placental abruption (Dayal, 1999).
Manning and coworkers (1993) published a remarkable description of 493 fetuses in which biophysical scores were performed immediately before measurement of umbilical venous blood pH values obtained via antepartum cordocentesis. Approximately 20 percent of tested fetuses had growth restriction, and the remainder had alloimmune hemolytic anemia. As shown in Figure 17-9, a biophysical score of 0 was almost invariably associated with significant fetal acidemia, whereas a normal score of 8 or 10 was associated with normal pH. An equivocal test result-a score of 6-was a poor predictor of abnormal outcome. As the abnormal score dropped from 2 or 4 down to 0, this decline was a more accurate predictor of abnormal fetal outcome. hus overall, these scores provide poor sensitivity to predict cord blood pH.