The only way for a doctor to know how the baby is tolerating the stressful process of labor and delivery is by monitoring its heart rate. Historically, doctors have been able to listen to the baby's heart rate using a standard or slightly modified stethoscope. In some countries, such devices are still the only means of monitoring the fetus' heart rate. Although these devices are simple to use and readily available, they permit only the most experienced doctor or nurse to notice marked changes in the fetus' heart rate-dramatic, short-term decreases in the fetus' heart rate called decelerations.

In the second half of the twentieth century, researchers began to monitor fetal heart rates continuously and print out the information. Currently, two different techniques are used to monitor the fetal heart rate electronically. These techniques allow the doctor to analyze a visual representation of rapid changes in the fetus' heart rate.

How Does the Fetal Heart Rate Monitor Work?

The fetal heart rate monitor is simply an electronic box that monitors to measure the fetal heart rate and contractions of the uterus. It counts the fetus' heartbeats and prints them out on a rolling sheet of paper, and displays the rate on a screen. A monitor allows doctors and nurses to distinguish between the ?lub? and the ?dub? beats of the fetus' heart so that a beat isn't counted twice. A very slow heart rate may fool the monitor into detecting a false heart rate. However, this is extremely rare.

Each fetal monitor screen has two channels. The top channel displays the fetal heart rate and the bottom channel displays the uterine contractions. Correlating the changes in the fetus' heart rate with the timing of the uterine contractions is more informative to the doctor or nurse than following the heart rate alone. There are two basic types of monitoring devices: external and internal fetal heart rate monitors.

What About the Old-fashioned Way of Monitoring?

A stethoscope is just as effective as a fetal heart rate monitor for picking up the more dramatic and important changes in the fetus' heart rate. Today, it is uncommon for women to forego electronic monitoring. However, studies have shown that in healthy mothers with uncomplicated pregnancies, babies who are monitored by listening carefully and often to the fetus' heart rate with a stethoscope have no increase in complications compared to babies monitored by continuous electronic fetal monitoring.