What are the key findings of a Modified Biophysical Profile (BPP)?

From the Guidelines

A Modified Biophysical Profile (BPP) is a prenatal assessment that combines non-stress test (NST) monitoring with amniotic fluid index (AFI) measurement to evaluate fetal well-being, with key findings including fetal heart rate reactivity and amniotic fluid volume, as outlined in the ACR Appropriateness Criteria assessment of fetal well-being 1. The key components of a Modified BPP include:

• Fetal heart rate reactivity, which is assessed through NST, with a reactive test showing at least two fetal heart rate accelerations of 15 beats per minute lasting 15 seconds within a 20-minute period 1
• Amniotic fluid volume, which is measured using either the maximum vertical pocket (MVP) or amniotic fluid index (AFI), with normal values varying by gestational age, but generally considered normal if the MVP is 2 cm or greater, or if the AFI is between 5-25 cm 1 A normal Modified BPP, indicated by a reactive NST and normal AFI, suggests a well-oxygenated fetus with minimal risk of acidemia, while abnormal results may necessitate additional testing or delivery depending on gestational age and clinical context, as noted in the Journal of the American College of Radiology 1. The Modified BPP is typically performed in the third trimester for high-risk pregnancies, including those with hypertension, diabetes, decreased fetal movement, intrauterine growth restriction, or post-term pregnancies, and is valuable because it evaluates both acute fetal status (heart rate) and chronic placental function (amniotic fluid), providing a comprehensive picture of fetal health, as discussed in the ACR Appropriateness Criteria assessment of fetal well-being 1. Some of the key points to consider when interpreting the results of a Modified BPP include:
• The definition of a reactive NST, which varies by gestational age, with accelerations of 15 beats per minute lasting 15 seconds required at 32 weeks or later, and accelerations of 10 beats per minute lasting 10 seconds required before 32 weeks 1
• The importance of amniotic fluid volume in assessing fetal well-being, with oligohydramnios (low amniotic fluid) potentially indicating intrauterine growth restriction, and polyhydramnios (high amniotic fluid) potentially indicating gestational diabetes or other maternal conditions 1 The Modified BPP is a valuable tool for assessing fetal well-being, particularly in high-risk pregnancies, and should be interpreted in the context of gestational age and clinical context, with abnormal results prompting further evaluation and potential intervention, as recommended by the ACR Appropriateness Criteria assessment of fetal well-being 1.

From the Research

Modified Biophysical Profile (BPP) Key Findings

• The modified biophysical profile is a combination of nonstress testing (NST) and ultrasound evaluation of amniotic fluid volume, and is used for antenatal fetal surveillance in high-risk pregnancies 2.
• Studies have shown that the modified biophysical profile is an effective means of fetal surveillance and can identify patients at increased risk for adverse perinatal outcomes and small-for-gestational-age infants 2, 3.
• The use of the modified biophysical profile has been associated with a lower incidence of perinatal morbidity and mortality compared to traditional methods of fetal surveillance 3.
• The modified biophysical profile has been compared to other methods of fetal surveillance, such as the contraction stress test and the biophysical profile, and has been found to be a reliable and effective means of assessing fetal well-being 3, 4.
• The rapid biophysical profile, which combines amniotic fluid index and sound-provoked fetal movement, has been found to be a reliable predictor of intrapartum fetal distress in high-risk pregnancies 5.
• The use of the single deepest pocket technique versus the amniotic fluid index during modified biophysical profile has been studied, and results have shown that the single deepest pocket technique is associated with a lower rate of suspected oligohydramnios 6.

Comparison of Techniques

• The modified biophysical profile has been compared to the biophysical profile, and results have shown that the modified biophysical profile is a more practical and effective means of assessing fetal well-being 2, 3.
• The contraction stress test has been compared to the biophysical profile as a backup test, and results have shown that there is no significant benefit to using the contraction stress test 3.
• The rapid biophysical profile has been compared to the nonstress test, and results have shown that the rapid biophysical profile is a more reliable predictor of intrapartum fetal distress 5.

Clinical Implications

• The modified biophysical profile can be used to identify patients at increased risk for adverse perinatal outcomes and small-for-gestational-age infants, allowing for early intervention and management 2, 3.
• The use of the modified biophysical profile can help to reduce the incidence of perinatal morbidity and mortality in high-risk pregnancies 3.
• The rapid biophysical profile can be used as a reliable and effective means of assessing fetal well-being in high-risk pregnancies, and can help to identify patients at risk for intrapartum fetal distress 5.