Biophysical Profile (BPP)

The Biophysical Profile (BPP) is an essential assessment tool in obstetrics used to evaluate fetal well-being, particularly in high-risk pregnancies.

It combines ultrasound monitoring and cardiotocography (CTG) to assess fetal health by scoring five parameters: fetal heart rate (non-stress test), fetal breathing movements, fetal movement, fetal tone, and amniotic fluid volume.

Each parameter is scored on a scale of 0 to 2, with a maximum total score of 10. A score of 8 to 10 is generally considered normal, 6 as equivocal, and 4 or less as abnormal, indicating potential fetal compromise. Here’s a detailed breakdown of each component:

1. Fetal Heart Rate Reactivity (Non-Stress Test)

• The non-stress test (NST) measures fetal heart rate acceleration in response to fetal movement.
• Scoring:
  • 2 points: At least two accelerations in a 20-minute period, each lasting at least 15 seconds and peaking at least 15 bpm above the baseline (for pregnancies ≥32 weeks). For pregnancies <32 weeks, 10 bpm above the baseline for at least 10 seconds is considered reactive.
  • 0 points: Fewer than two accelerations, or accelerations do not meet the required parameters.
• Clinical significance: A reactive NST indicates normal autonomic function, while a non-reactive NST may suggest fetal hypoxia, acidosis, or sleep state.

2. Fetal Breathing Movements

• These movements are visualized as rhythmic movements of the diaphragm.
• Scoring:
  • 2 points: At least one episode of fetal breathing lasting at least 30 seconds within a 30-minute observation period.
  • 0 points: Absence of breathing movements or episodes lasting less than 30 seconds.
• Clinical significance: The presence of fetal breathing movements suggests an intact brainstem and adequate oxygenation. Their absence may be a sign of fetal compromise or hypoxia.

3. Fetal Movement

• This parameter evaluates gross body movements, such as limb or trunk movements.
• Scoring:
  • 2 points: At least three discrete body or limb movements within 30 minutes.
  • 0 points: Fewer than three movements observed in 30 minutes.
• Clinical significance: Reduced fetal movements are associated with hypoxia, CNS depression, or compromised fetal health.

4. Fetal Tone

• Assesses the presence of flexion and extension movements of limbs or trunk.
• Scoring:
  • 2 points: At least one episode of active extension and return to flexion of a limb or trunk.
  • 0 points: Slow extension with no return to flexion or absent movements.
• Clinical significance: Good fetal tone reflects normal neurologic function, whereas diminished tone may indicate CNS depression.

5. Amniotic Fluid Volume

• Evaluation is based on the largest single vertical pocket of amniotic fluid in each quadrant.
• Scoring:
  • 2 points: A single vertical pocket measuring at least 2 cm in depth.
  • 0 points: The absence of a pocket of at least 2 cm.
• Clinical significance: Amniotic fluid volume is a long-term indicator of fetal well-being. Oligohydramnios (low fluid) can be associated with fetal hypoxia, growth restriction, or placental insufficiency.

Clinical Applications

• BPP is commonly indicated in pregnancies with risk factors such as diabetes, hypertension, intrauterine growth restriction (IUGR), post-term pregnancy, and conditions with reduced fetal movements.
• It is used to guide clinical decisions regarding timing of delivery, especially in the setting of suspected fetal compromise. A score of 8–10 (with normal amniotic fluid) is generally reassuring, while scores of 6 or less may warrant further evaluation or even delivery, depending on gestational age and clinical scenario.
• BPP may be repeated weekly or biweekly depending on the specific maternal-fetal condition.

Advantages and Limitations

• Advantages: The BPP is non-invasive, provides immediate results, and assesses both acute and chronic fetal health indicators.
• Limitations: Results can be influenced by maternal medication, sleep cycles, or technical challenges. The test can be time-consuming and less predictive if performed by inexperienced personnel.

Modified Biophysical Profile

• The Modified BPP (mBPP) combines the NST with the assessment of amniotic fluid volume, providing a quicker assessment. It is considered a practical alternative with high predictive value for fetal well-being.

Clinical Decision-Making Based on BPP Scores

• BPP 8-10 (normal): Reassuring, continue routine antenatal care.
• BPP 6: Equivocal; further evaluation may include a repeat test within 24 hours or additional surveillance with Doppler studies.
• BPP ≤4: Considered abnormal, indicating a high risk of fetal compromise; immediate delivery is often recommended if the pregnancy is beyond 34 weeks or if fetal lung maturity is confirmed.

Role of Doppler Ultrasound in BPP

• Doppler studies, especially of the umbilical artery, can complement BPP findings in high-risk pregnancies by assessing placental circulation and fetal blood flow patterns.

Interpretation in Specific Clinical Scenarios

• IUGR: The presence of oligohydramnios with a low BPP score in an IUGR fetus indicates a higher risk of adverse outcomes.
• Diabetes: BPP is especially valuable in pregestational diabetes with vascular involvement, where placental function may be compromised.
• Post-term Pregnancy: BPP helps assess fetal status when the risk of placental insufficiency increases.

Emerging Trends

• The integration of advanced imaging techniques, such as three-dimensional ultrasound, and AI algorithms to improve the accuracy and efficiency of BPP.
• The role of adjunct tests like MRI and placental elastography in further refining fetal well-being assessments in complex cases.