What is specialized fetal testing?
Specialized fetal testing (the term 'fetus' refers to the developing baby in the uterus from the ninth week of pregnancy until the end of pregnancy) helps to check the baby's health, level of activity and growth during pregnancy. It is most often carried out when the mother's health problems, or problems that arise during pregnancy, increase the risk of stillbirth. If the test results suggest there may be a problem, you may need further tests or special care. Sometimes the baby may need to be born earlier than expected.
Why might I need specialized fetal tests?
If you have certain medical conditions, you may need frequent tests during your pregnancy to check your baby's health. These conditions include the following:
- Blood disorders
- Thyroid disease
- Heart disease
- Lupus
- Kidney disease
- Diabetes
- High blood pressure
Special tests in pregnancy are also carried out when problems arise during the pregnancy itself. The following pregnancy-related problems may signal a need for more frequent monitoring:
- High blood pressure during pregnancy
- Decreased fetal movement
- Too much or too little amniotic fluid
- Fetal growth problems
- A post-term pregnancy
- Rhesus (Rh) sensitization
- A previous fetal death
- A multiple pregnancy, if there are complications
What types of specialized fetal test are there?
The tests used to monitor fetal wellbeing include fetal movement counting, ultrasound, Doppler ultrasound of the umbilical or another artery, the non-stress test, the biophysical profile and the contraction stress test.
When are specialized fetal tests carried out?
Specialized fetal testing usually begins when a problem is suspected, or after the 32nd week of pregnancy. Your doctor decides when to start on the basis of the following factors:
- Whether the baby could survive if born early.
- How serious the mother's condition is.
- The risk of stillbirth
What is fetal movement counting?
If you have felt your baby moving less often, your doctor may ask you to keep track of the number of fetal movements (also called 'kick counts'). One way to do kick counts is to lie on your side and note how long the baby takes to make 10 movements. If it takes less than 2 hours, the result is reassuring — meaning that for now there do not appear to be any problems.
What is an obstetric ultrasound examination?
Ultrasound is a way of examining the baby using sound waves. It may be performed by your doctor or by a specially trained sonographer. During the examination the sound waves are produced by a device called a transducer. This is moved gently over your abdomen, or inserted into your vagina, while you are sitting or lying down. The sound waves create images that appear on a computer screen for the operator to see. If the results are 'non-reassuring' — meaning that more information is needed to be sure that all is well — other tests may be done.
What is Doppler ultrasound of the umbilical artery?
Doppler ultrasound is used to check the blood flow in the umbilical artery, a blood vessel in the umbilical cord. It is used together with other tests when the baby is not growing well, or where the baby is at risk of anemia, as in Rh sensitization.
How is Doppler ultrasound performed?
A transducer is moved gently over your abdomen to send out sound waves. An image of the artery being examined appears on a computer screen. If the test shows problems with the blood flow in the placenta, it may mean that the amount of nutrients and oxygen reaching the fetus is reduced.
What is the non-stress test?
The non-stress test is the commonest specialized fetal test. It measures the baby's heart rate in response to its own movements, and is done to assess the baby's wellbeing.
How is the non-stress test performed?
For this test two belts are placed across your abdomen: one has sensors that measure the fetal heart rate, the other has sensors that detect contractions of the uterus. You are asked to mark when the baby moves by pressing a button, which shows on the fetal heart rate trace when a movement has occurred.
What is the biophysical profile (BPP)?
A biophysical profile may be done if a woman is past her due date, or if she has a condition that causes problems with fetal growth or with the amniotic fluid. It helps assess the baby's wellbeing in these five areas:
1. Fetal heart rate
2. Fetal breathing movements
3. Fetal body movements
4. Fetal muscle tone
5. The amount of amniotic fluid
What is a modified BPP?
The modified BPP combines a non-stress test with an assessment of the amniotic fluid by ultrasound. The fetal heart rate is monitored in the same way as in the non-stress test. Ultrasound is used to measure the depth of the amniotic fluid in the uterus. If the level of amniotic fluid is low, it may mean there is a problem with the blood flow in the placenta.
What is the contraction stress test?
The contraction stress test assesses how the fetal heart rate responds when the uterus contracts. It is sometimes used if a non-stress test result is non-reassuring. For this test, belts with sensors that detect the fetal heart rate and the contractions of the uterus are placed on your abdomen. To make your uterus contract gently, you may be asked to rub your nipples through your clothing, or you may be given oxytocin intravenously. Your uterus may contract on its own, especially if the test is done late in pregnancy. A fall in the heart rate after most contractions is a non-reassuring result.
Are there risks associated with the contraction stress test?
For some women this test can increase the risk of complications. The contractions could start labor if you are at risk of preterm birth. The test can also cause bleeding if you have a condition called placenta previa, or certain other conditions.