Biophysical Profile (BPP) advantage is that assessment of variable factors of fetal biophysical activity are more reliable than examination of a single parameter (e.g., fetal heart rate). Indications for BPP include postdate pregnancy, maternal hypertension, diabetes mellitus, vaginal bleeding, maternal Rh factor sensitization, maternal history of stillbirth, and premature rupture of membranes. The BPP is probably more useful in identifying a fetus that is in jeopardy than in predicting future fetal well-being. Testing usually begins at about 32 weeks, but can be done earlier if maternal complications exist.
The Biophysical Profile is a method of evaluating antepartal fetal status on the basis of five variables: fetal heart rate, fetal breathing movement, gross fetal movement, fetal muscle tone, and amniotic fluid volume. Fetal heart rate reactivity is measured with the nonstress test; the other four parameters are measured with ultrasonography. Each variable is scored as either 2 or 0. Therefore 10 is a perfect score, and 0 is the lowest score.
- Fetal heart rate reactivity. Fetal heart rate reactivity is measured and interpreted in the same way as with the nonstress test. Fetal heart rate is considered reactive when there are movement-associated fetal heart rate accelerations of at least 15 beats/min above baseline and 15 seconds in duration, over a 20-minute time period. A score of 2 indicates reactivity; a score of 0 indicates that the fetal heart rate is nonreactive.
- Fetal breathing movements. This variable is assessed on the assumption that fetal breathing movements indicate fetal well-being, and their absence may indicate hypoxemia. Rate and uniformity of fetal breathing become increasingly regular after week 36 of gestation. At least one episode of fetal breathing lasting a minimum of 60 seconds within a 30-minute observation period is scored as 2; absence of this breathing pattern is scored as 0. Several factors can alter fetal breathing movements. For example, fetal breathing movements increase during the second and third hours after maternal meals and also at night. Fetal breathing movements may decrease in conditions such as hypoxemia, hypoglycemia, nicotine use, and alcohol ingestion.
- Fetal body movements. Fetal activity is a reflection of neurologic integrity and function. The presence of at least three discrete episodes of fetal movement within a 30-minute observation period is scored as 2; two or fewer fetal movements in 30 minutes is scored as 0. Fetal activity is greatest 1 to 3 hours after the mother has consumed a meal. For this reason, it is often suggested that this test be scheduled in relation to mealtime.
- Fetal muscle tone. In the uterus, the fetus is normally in a position of flexion, but also stretches, rolls, and moves. The arms, legs, trunk, and head may be flexed and extended. If there is at least one episode of active extension with return to flexion (e.g., opening and closing of a hand), it is scored as 2; slow extension with return to only partial flexion, fetal movement not followed by return to flexion, limbs or spine in extension, and an open fetal hand are scored as 0.
- Amniotic fluid volume. Measurement of amniotic fluid volume is an effective method of predicting fetal distress. Oligohydramnios (too little amniotic fluid) has been associated with fetal anomalies, intrauterine growth restriction, and postterm pregnancy. Immediate delivery is recommended in postterm pregnancy with oligohydramnios because of the high risk of associated problems such as umbilical cord compromise. If there is at least one pocket of amniotic fluid that measures 1 cm in two perpendicular planes, the score is 2; if fluid is absent in most areas of the uterine cavity or else the largest pocket measures 1 cm or less in the vertical axis, the score is 0. A score of 8 or 10 with an acceptable amount of amniotic fluid is normal. A score of 8 with oligohydramnios or a score of 4 to 6 is equivocal and is interpreted as possibly abnormal. Some clinicians recommend repeating the test within 24 hours; others advocate extending testing after any equivocal test result. A score of 0 or 2 is abnormal and indicates the need for assessment of immediate delivery.
Although the Biophysical Profile is fairly new, it has already been modified. Some physicians omit the nonstress test if the ultrasound parameters are normal; some include placental grading as a sixth parameter. Information about fetal size, position, and location of the placenta can also be obtained.
Another measure of fetal well-being is the amniotic fluid index (AFI). This is determined by using ultrasound to measure the largest collection of amniotic fluid in each of the four quadrants within the uterus. The sum represents a number that is plotted on a graph in which the age of gestation is also taken into account. If the AFI is less than 2.4 percentile, oligohydramnios is present. If AFI exceeds the 97 percentile, polyhydramnios exists. An abnormal amniotic fluid index observed in antepartum testing is associated with an increased risk of intrauterine growth restriction and overall adverse perinatal outcome. Some suggest that borderline amniotic fluid index be performed twice weekly. Yet other studies have shown AFI to be so weak a predictor for poor neonatal outcome as to be useless. The percentile value seems to be a better indicator than an absolute fluid volume. Oligohydramnios is associated with placental failure or fetal renal problems. Polyhydramnios is associated with maternal diabetes or fetal upper gastrointestinal malformation/obstruction.
Additional information about fetal well-being can be gained from Doppler ultrasound evaluation of the placenta and the umbilical artery flow velocity. Changes in umbilical artery flow or direction may indicate fetal stress or illness.
Normal Biophysical Profile Scores
After examining all the variable, a normal total would be between 8 and 10. Immediate delivery may be considered if the total score is less than 4.
Causes of Biophysical Profile False Indications
- Maternal Hyperglycemia may increase fetal biophysical activity.
- Hypoxemia and Trauma may decrease fetal biophysical activity.
- Maternal or fetal infection will affect fetal biophysical activity.
- Occasionally no movement will be noted. If no eye movement or respiratory movement is noted, the fetus may be sleeping.
- Central nervous system stimulants, such as Catecholamines, can increase fetal biophysical activity.
- Magnesium Sulfate, Analgesics, Anesthetics, Sedatives, and Nicotine can depress fetal biophysical activity.
Findings of Biophysical Profile
The following conditions may be detected as the Biophysical Profile is performed:
- Fetal Asphyxia.
- Congenital Anomalies.
- Intrauterine Growth Restriction.
- Postterm Pregnancy.
- Fetal Distress or Death.