Prenatal visits are essential throughout pregnancy, as they allow constant monitoring and care for your unborn baby. Such consultations involve a routine physical examination with your midwife or obstetrician. In most cases, you may be requested to undergo several prenatal tests. This may include a nonstress test, also known as fetal heart rate monitoring.
A nonstress test is a common prenatal test that allows you to check the baby’s health further.1 This test generally monitors the baby’s heart rate in response to its movements. Pregnant mothers often need nothing to worry about. As the name suggests, no stress is placed on the fetus while the test is performed.
Why It’s Done
The healthcare team can gather essential information regarding the baby’s oxygen supply by monitoring its heart rate and how it responds during movement. Like an adult’s, the baby’s heart rate typically beats faster during activity, especially later in pregnancy. The test will monitor heart rate variability in response to fetal movement.
Otherwise, the baby could be experiencing fetal hypoxia—a condition where they do not get adequate oxygen. With a nonstress test, your doctor can decide whether there is a need to do further monitoring, testing, or intervention to prevent fetal death.
Who It’s For
Not all pregnant women may be required to undergo a nonstress test. Your doctor may still suggest it if you have certain complications throughout your pregnancy.2 These can include gestational diabetes, heart disease, preeclampsia, or a postdate pregnancy. A nonstress test can also be recommended if you have had an amniocentesis or have been diagnosed with low amniotic fluid.
Your baby needs to be at a certain weight, depending on their gestational age. If the baby measures small and isn’t very active, then a nonstress test may be performed. It is also performed when you are past your baby’s due date, yet you haven’t gone into labor. Usually, the test is done during your third trimester of pregnancy, which is from week 28 onwards.
How it’s Performed
During a nonstress test, belts are strapped across the mother’s abdomen and connected to two different transducers—the Doppler to measure the baby’s heart rate and the toco transducer to measure the contractions. Toco transducers work by measuring the relative rate, strength, and uterine contractions duration.3 These are the same fetal monitors you will likely be hooked to during labor if you are planning a hospital birth.
The entire test measures the heart rate, movement, and reactivity of the fetal heart rate to movement. It will go on for about 20 to 30 minutes. If the baby does not move, it does not immediately indicate a problem, as they could be asleep. Your healthcare provider may use a small “buzzer” to alert the baby while the test is performed. You may also be encouraged to drink some juice or eat something sugary to prompt the baby to move and get excited!
What the Results Mean
A reactive nonstress test results when the baby’s heart rate rises normally during movement. This means that the baby is receiving adequate oxygen and blood flow.
Meanwhile, a non-reactive result means that the baby’s heart rate did not increase enough during a minimum number of movements within a 40-minute period, which may require further observation and more tests to check your baby’s health further, such as a biophysical profile or a contraction stress test. In more serious cases, your doctor may recommend labor induction and early delivery, especially in the case of a non-reactive result during week 39 or a full-term pregnancy.
A nonstress test may be something you have not heard of until today. Make it a point to be on top of your prenatal consultations by discussing prenatal tests in-depth and what they might mean for you and your little one!