Monitoring Fetal Health with Special Tests

Reviewed by James Brann, MD
Special tests may be done during pregnancy when your baby is at a greater risk of problems either resulting in pregnancy complications or those leading to stillbirth. This may occur when these things happen:
  • Your baby has decreased movements or stops moving
  • You are pregnant with multiples and have certain complications
  • You are pregnant past week 42 (post term pregnancy)
  • You have problems including Rh sensitization, high blood pressure or fetal growth problems
  • You have a high-risk pregnancy (you have preexisting health conditions like heart disease or diabetes, or had complications during a previous pregnancy)

Special tests

If special tests need to be performed, it usually begins between pregnancy weeks 32-34. If problems appear serious or include multiple risk factors, testing may begin even earlier.

How often these tests are done will depend on the condition which led to the testing, whether the specific condition stays stable, and the results of the tests. Some tests are done every week, while others may be done twice a week.

Tests used in monitoring fetal health include the non stress test, biophysical profile, and modified biophysical profile. In addition, tests include fetal movement counts, Doppler ultrasound of the umbilical artery and the contraction stress test.

Non stress test

This measures the baby’s heart rate in response to movement. Nothing is done which would stress the baby during the test.

This type of test may be performed in your doctor’s office or in a hospital. During the test, a mother is either lying down or reclining, and the test takes about 20 minutes, or so. A special belt with a sensor goes around a woman’s abdomen, measuring the baby’s heart rate, which is then recorded by a machine.

If there are at least two accelerations within 20 minutes, this means the result is reactive or reassuring. Reactive means there aren’t any problems, for now. Nonreactive is when there aren’t enough accelerations detected over 40 minutes. This may mean your baby was sleeping. If this occurs, the test may last for another 40 minutes, or your doctor may use sound to help stimulate your baby to move by projecting it over your abdomen. Nonreactive results may happen if you have taken certain medications. It may also mean your baby isn’t getting enough oxygen.

Biophysical profile

This may be used when the test results from other methods are nonreassuring. It uses scoring to evaluate a baby’s well being in five areas. Each area gets a score between 0 and 2, with up to a total of 10 points. These include:
  • Fetal body movements
  • Fetal heart rate
  • Fetal breathing movements
  • Fetal muscle tone
  • Amount of amniotic fluid
Also called BPP, it involves monitoring a baby’s heart rate just like a non stress test, as well as doing an ultrasound. During this type of exam, a transducer rolls carefully over your abdomen while you are either lying down or reclining. This creates sound waves, which bounce off the body’s internal structures. The transducer takes the echoes and coverts them into images on a computer screen for viewing.

A reassuring score is anywhere from 8-10. A score of six is not reassuring, nor is it nonreassuring. In this case, you may have another BPP done within the next 12 to 24 hours, or your doctor may want to deliver your baby. If your score is four or less, you need more testing. It sometimes means a baby also needs to be delivered immediately.

No matter the score, if there’s not enough amniotic fluid, either you may need to consider delivery, or more frequent testing needs to be done.

Modified BPP

This is performed for the same reasons that a BPP is performed. This combines the non stress test with amniotic fluid assessment, performed with an ultrasound. It may be equally as useful as BPP in predicting a baby’s well being.

The baby’s heart rate is monitored the same way it was with the non stress test. Ultrasound measures how much amniotic fluid is found in four areas of a woman’s uterus.

If the results of this test are nonreactive, it may mean your baby isn’t getting all the oxygen they need. The results of amniotic fluid measurement tell how well the placenta is working. If the amniotic fluid level’s low, it may mean there are problems with blood flowing in the placenta. A contraction stress test or full BPP may be needed to help confirm the test results.

Fetal movement counts

If you’re feeling your baby move less than normal, your doctor may want you to keep track of your baby’s movements. Also called kick counts, fetal movement counting is something you can do at home. There are different ways to do it. Your doctor will tell you how often to do the test, and when to call them about the results.

Doppler ultrasound exam of umbilical artery

This is used in checking the blood flowing in the umbilical artery. This type of blood vessel is found in the umbilical cord. A Doppler ultrasound may be used along with other tests when a baby shows signs it isn’t growing well.

During this test, you will be lying down or reclining. Doctors will roll a transducer carefully over your abdomen in order to project sound waves. An image of the artery will then come up on a computer screen.

With a normal test, blood flows normally in the umbilical artery. If the test is showing problems with blood flowing in the placenta, it may indicate a decreased amount of oxygen is going to your baby.

Contraction stress test

This type of stress allows your doctor to see how your baby’s heart rate reacts when your uterus contracts. This is sometimes used if other tests come back unclear or positive.

With the contraction stress test, your nurse or doctor puts belts with sensors on them across your abdomen. These sensors detect your uterine contractions and your baby’s heart rate. In order to make your uterus contract just mildly, you may need to rub your nipples through your clothing, or take oxytocin.

If your baby’s heart rate doesn’t go down after a contraction, you have a negative result (normal). When your baby’s heart rate goes down after contractions, the result is positive. This is when your doctor is concerned. Results may also not be clear or they’re unsatisfactory, meaning there weren’t enough contractions to get a good result.

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