A fetal stress test is done on pregnant women to measure the baby's heart rate and movement. The test consists of placing two belts on the woman's belly. One measures fetal heart rate and the other measures contractions. This type of test usually takes 20 to 30 minutes to perform and is given to women who are at least 28 weeks pregnant.
Doctors may administer a fetal stress test if the mother is concerned that the baby is not moving as often as usual or not moving at all. A fetal stress test may also be done if a pregnant woman is past her due date or if there is a problem with the placenta. If the mother-to-be is having a high-risk pregnancy, complications of any kind may require this exam.
Problems with the placenta or umbilical cord can often cause less oxygen to get to the baby. A fetal stress test can detect these problems. Placental and umbilical cord problems detected on a fetal stress test can also be indicators of more severe fetal distress.
Doctors doing the test look for the baby's heart rate to respond to movement. A healthy baby's heart rate will increase during movement and decrease at rest. If this is the case, the baby is getting the right amount of oxygen. However, when oxygen levels are low, the baby will not respond properly to movement.
Women who are 28 weeks pregnant or older are candidates for fetal stress testing. Doctors usually don't do the test sooner because the fetus isn't developed enough to respond to the test. Fetal stress testing is a non-invasive procedure that is free of risks or side effects for both the woman and the baby.
Most tests are done in the doctor's office. The nurse or doctor will attach fetal monitoring equipment to the woman's belly and record the baby's heart rate and movement. Some equipment may allow the pregnant woman to press a button when she feels the baby move. This helps doctors see the relationship between movement and heart rate.
Sometimes babies will not cooperate with the test. If the baby is not moving, the woman can be offered a drink with sugar or carbonation to wake the baby. Creating a loud sound is another option used to encourage the baby.
The results of a fetal stress test are classified as reactive or nonreactive. Reactive means that the blood flow and oxygen levels reaching the baby are in the correct range. A nonreactive result will usually result in further testing to determine the reason for the lack of fetal movement. Possible reasons for a nonreactive result include poor oxygenation, sleep patterns, prescriptions taken by the pregnant woman, or over-the-counter medications.