The Biophysical Profile (BPP) is a non-invasive prenatal test used primarily during the third trimester of pregnancy to assess fetal well-being. This diagnostic tool combines a real-time ultrasound and a Non-Stress Test (NST) to evaluate the fetus’s overall health and oxygen supply in the womb. The BPP assigns points to observable biological activities, providing a quantifiable measure of central nervous system function. By assessing multiple variables, the test helps clinicians determine if the fetus is experiencing distress or a lack of oxygen before birth.
Why the BPP Test is Performed
A healthcare provider typically orders a BPP when there is an increased risk of complications affecting the fetus’s environment or placental function. Common reasons include maternal health conditions, such as chronic hypertension, gestational diabetes, or preeclampsia, which can compromise the flow of nutrients and oxygen. Decreased fetal movement reported by the mother is also a frequent indication, as it may signal inadequate oxygen or energy supply.
The test is also routinely used when a pregnancy progresses beyond the estimated due date, typically past 41 weeks, to monitor the post-term fetus. The BPP provides a detailed picture of the fetus’s physiological status when growth restriction is suspected or when amniotic fluid appears too low (oligohydramnios). A healthy fetus exhibits expected patterns of movement and heart rate, which are disrupted if the oxygen supply is reduced.
The Five Key Components of the Test
The complete BPP evaluates five distinct biophysical variables: four assessed by ultrasound and one by external monitoring. These variables reflect the fetus’s neurological and physical condition, which are sensitive to changes in oxygen levels. Each component is observed over a 30-minute period and is assigned a score of either 2 points for a normal result or 0 points for an abnormal result.
Fetal Breathing Movements
The sonographer looks for at least one episode of rhythmic breathing that lasts 30 seconds or longer.
Gross Body Movements
This requires observing at least three separate movements of the body or limbs within the 30-minute window.
Fetal Tone
Tone is assessed by watching for one or more episodes of active extension of a limb or the trunk with an immediate return to a flexed position.
Amniotic Fluid Volume (AFV)
AFV is considered an indicator of long-term placental function. A normal score is given if the deepest vertical pocket of fluid measures more than 2 centimeters, suggesting healthy blood flow to the fetal kidneys.
Non-Stress Test (NST)
The NST is performed using external electronic fetal monitoring, not ultrasound. For a normal score, the NST must show a “reactive” heart rate, meaning the fetal heart rate increases temporarily at least twice in 20 minutes in response to movement.
Understanding the BPP Scoring System
The five components are combined to produce a total score out of a possible 10 points. A lower score indicates a greater possibility of fetal compromise. A score of 8/10 or 10/10 is considered reassuring and is associated with a low risk of fetal death within the following week. This score suggests the fetus is well-oxygenated and the central nervous system is functioning appropriately.
A score of 6/10 is considered equivocal or borderline, which means the result is uncertain and requires further evaluation. This result often prompts the healthcare provider to repeat the BPP within 12 to 24 hours to check for improvement or deterioration. Scores of 4/10 or less are considered concerning and suggest a possible issue with oxygenation that requires immediate attention. The sequential loss of scoring points, starting with a nonreactive NST and loss of breathing movements, is often the first sign of progressive oxygen deprivation.
Next Steps After Receiving Results
The management plan following a BPP is guided by the total score, the fetus’s gestational age, and the overall clinical picture. For a reassuring score of 8 or 10, the typical next step is a continuation of routine prenatal care. A normal result is highly reliable in predicting the absence of fetal distress for the immediate future, though repeat testing may be scheduled based on the initial reason for the BPP.
When the score is equivocal at 6/10, especially in a pregnancy near term, delivery may be considered after further evaluation. If the pregnancy is not yet near term, the BPP may be repeated within a day to see if the fetus’s condition has improved. A significantly low score of 4/10 or less often leads to a recommendation for expedited delivery, either through induction of labor or a Cesarean section, depending on the gestational age and other factors. The BPP serves as a valuable clinical tool, but the final decision regarding intervention always takes into account the specific circumstances of the mother and the fetus.