During late pregnancy and during labor, your doctor may want to monitor the fetal heart rate and other functions. Fetal heart rate monitoring is used to check the rate, rhythm, and the presence or absence of increases or 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.
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/or 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.
Fetal monitoring is widely used. There are no known risks to using the fetoscope, Doppler, or external monitoring. There may be a slight risk of infection with internal monitoring. The scalp electrode may also cause a mark or small cut on the baby's head, but this usually heals quickly. An abnormal fetal heart rate pattern does not always mean the fetus is in danger. Electronic fetal monitoring is widely used in the United States. However, studies have found that the use of electronic fetal monitoring is associated with a greater chance for vacuum and forceps use with vaginal deliveries, and for cesarean delivery.
Fetal monitoring may help with possible recognition of problems in the fetus. Other testing or delivery may be necessary.