Which procedure evaluates the effects of fetal movement on fetal heart activity?

• Overview
• Test Details
• Results and Follow-Up
• Additional Details

Overview

What is the biophysical profile?

The biophysical profile is a noninvasive prenatal diagnostic test that usually is performed after the 28th week of pregnancy to evaluate the well-being of the fetus. It combines an ultrasound examination with a nonstress test. The nonstress test is performed to assess fetal heart rate acceleration in response to movement. The ultrasound test is designed to assess four components:

• Fetal gross body movement: Separate movements of the body or limbs, including fine motor movements
• Fetal muscle tone: Opening or closing of the hands and mouth, extension and flexing of the limbs, or repositioning or rotation of the trunk of the body
• Fetal breathing movements: Continuous, rhythmic breathing episodes
• Amniotic fluid volume: A single pocket of amniotic fluid that measures at least one centimeter across and two centimeters vertically

In some cases, a modified biophysical profile may be performed instead of the complete biophysical profile. The modified biophysical profile combines a nonstress test with an ultrasound assessment of the amount of amniotic fluid.

Test Details

Why is the biophysical profile performed?

The biophysical profile may be ordered for people with high-risk pregnancies, pregnancies that last beyond 40 weeks, or in other situations where there may be complications during gestation.

The indications for a biophysical profile include

• Long-term maternal diseases, such as hypertension, lupus, renal disease, or thrombocytopenia.
• Decrease in fetal movement.
• Previous stillbirth or other negative outcome.
• Multiple gestation (more than one fetus).
• Pregnancy-related hypertension (high blood pressure) or preeclampsia.
• Possible intrauterine growth restriction.
• Diabetes before pregnancy or diabetes associated with pregnancy (gestational diabetes).
• Late term pregnancy (at or beyond 41 weeks).
• Moderate or severe asthma.

How is the biophysical profile performed?

Fetal movements and muscle tone are monitored over a period of at least 30 minutes. The biophysical profile consists of a nonstress test and an ultrasound exam.

• Nonstress test: An electronic fetal monitor is used to measure the fetal heart rate while you're reclining or lying down. A belt with an electronic sensor is placed around her abdomen. During that time, the fetal heart rate is measured and recorded. The test usually takes about 20 minutes. There should be two or more accelerations of the fetal heart rate. If there are fewer than two, it may indicate that the fetus is asleep. In that case, the fetus may be “awakened” with a buzzer or a loud noise to stimulate movement. The nonstress test may be done in a doctor’s office or a hospital.
• Ultrasound examination: The ultrasound exam is also performed when you're reclining or lying down. A device called a transducer is gently applied over your abdomen to produce sound waves that echo off the internal structures of your body. The transducer converts the echoes to images that can be viewed on a computer screen. It takes about 30 minutes to complete the examination.

Results and Follow-Up

How are components scored during the biophysical profile?

The biophysical profile will yield a maximum score of 10 points, if all criteria are satisfied. Each of the components receives a score of two points, unless the results are abnormal. The criteria for each component are listed below.

• Nonstress test: At least two episodes of fetal heart rate acceleration during a 20-minute period.
• Fetal gross body movement: Three or more separate movements of the fetal body or limbs over 30 minutes.
• Fetal muscle tone: One or more episodes of active extension and flexion of an arm or leg, or the opening and closing of a hand, during the 30-minute test.
• Fetal breathing movements: At least one episode of continuous fetal breathing that lasts at least 30 seconds during the 30-minute test.
• Amniotic fluid volume: A single pocket of amniotic fluid that measures at least one centimeter across and two centimeters vertically.

Any component that does not meet the criteria shown is considered abnormal and receives a score of zero points.

What does the biophysical profile test score indicate?

A total score of 10 points or eight out of 10 points with normal amniotic fluid volume is regarded as normal. A score of six indicates that there may be problems that require further evaluation or monitoring. If the pregnancy is at or beyond 37 weeks, delivery may be considered. The biophysical profile should be repeated within 24 hours if the pregnancy is less than 37 weeks.

A score of less than eight may suggest that the fetus is not receiving enough oxygen (fetal asphyxia). However, it can also be lower when certain drugs such as corticosteroids are administered during pregnancy.

If the biophysical profile yields a score of four or less, delivery should be induced. If the period of gestation is less than 32 weeks and the score is four, further evaluation and monitoring of the pregnancy may be necessary.

Overall, a low score indicates a greater risk of stillbirths and fetal asphyxia.

For the modified biophysical profile, results are considered normal if the nonstress test is reactive (normal) and the pocket of amniotic fluid measures more than two centimeters.

Additional Details

What are the advantages and drawbacks of the biophysical profile?

The advantages of the biophysical profile include:

• Minimal risk to the fetus and person who is pregnant.

The drawbacks include:

• Lower reliability if the fetus is severely premature. The test should not be performed before the 24th week of pregnancy.
• Results may be affected by use of corticosteroids. The rate of fetal breathing and movement may be diminished for several days after a pregnant person is treated with corticosteroids.
• The test may need to be done again in some cases.

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