Non-stress/contraction Stress Tests (fetal heart rate testing)
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What is fetal monitoring?
During late pregnancy and during labor, your doctor may want to monitor the fetal heart rate and other functions.
Fetal heart rate monitoring is a method of checking the rate, rhythm, and the presence or absence of accelerations (increases) or decelerations (decreases) of the fetal heartbeat. It also checks how much the fetal heart rate changes around the baseline. The average fetal heart rate is between 110 and 160 beats per minute. The fetal heart rate may change as the fetus responds to conditions in the uterus. An abnormal fetal heart rate or pattern may mean that the fetus is not getting enough oxygen or there are other problems. An abnormal pattern also may mean that an emergency cesarean delivery is needed.
How is fetal monitoring performed?
Using a handheld Doppler (a type of ultrasound) to listen to the fetal heartbeat is the most basic type of fetal heart rate monitoring. This is often used during prenatal visits to count the fetal heart rate or in a pregnancy less than 24 weeks. Electronic fetal monitoring is used in late pregnancy to evaluate the fetus or to check fetal well-being during labor. Although the specific details of each procedure vary slightly, generally, electronic fetal monitoring follows this process:
- Gel is applied to the mother's abdomen to act as a medium for the ultrasound transducer.
- The ultrasound transducer is attached to the abdomen with straps and transmits the fetal heartbeat to a recorder. The fetal heart rate is displayed on a screen and printed onto special paper.
- During contractions, an external tocodynamometer (a monitoring device that is placed over the top of the uterus with a belt) can record the patterns of contractions.
- Sometimes, internal fetal monitoring is necessary for a more accurate reading of the fetal heart rate. Your bag of waters (amniotic fluid) must be broken and your cervix must be partially dilated to use internal monitoring. Internal fetal monitoring involves inserting an electrode through the dilated cervix and attaching the electrode to the scalp of the fetus, called a fetal scalp electrode.