The fetal biophysical profile score (BPS or BPP) refers to the sonographic assessment of four discrete biophysical variables:
- Fetal movement
- Fetal tone
- Fetal breathing
- Amniotic fluid volume
- Results of nonstress testing
Each of these five parameters is given a score of 0 or 2 points, depending upon whether specific criteria are met (table 1). The presence of these biophysical variables implies absence of significant central nervous system hypoxemia/acidemia at the time of testing. By comparison, a compromised fetus typically exhibits loss of accelerations of the fetal heart rate (FHR), decreased body and breathing movements, hypotonia, and, less acutely, decreased amniotic fluid volume.
The clinical value of the cumulative fetal BPS is that it is noninvasive, easily learned and performed, and an accurate means for predicting the presence of significant fetal acidemia, which is the most common cause of fetal death or damage . Seventy to 90 percent of late fetal deaths display evidence of chronic or acute and chronic compromise prior to demise . Sonographic detection of signs of fetal compromise can allow appropriate intervention that ideally will prevent adverse fetal sequelae.
Although the use of biophysical testing schemes to monitor high-risk pregnancies has become routine, this practice pattern has evolved with limited high quality scientific data to support its use . Moreover, there are no randomized trials on which to base recommendations for the best initial testing approach for specific types of high-risk pregnancies, the optimal timing of test initiation, the frequency of testing based on test results, conditions that may affect test results, and the effect of gestational age.