It is a crude measure of the strength and frequently of contractions. Fetal monitoring is the basis for the non-stress test and the oxytocin challenge test described below. It is often used to confirm the well-being of the fetus based on the principle that a healthy fetus will demonstrate an acceleration in its heart rate following movement such as rubbing the mother's abdomen or making a loud noise above the abdomen with a special device. When movement of the fetus is noted, a recording of the fetal heart rate is made. If the heart rate goes up, the test is normal.
Labor represents a stress to the fetus.
Every time the uterus contracts, the fetus is momentarily deprived of its usual blood supply and oxygen. This is not a problem for most babies. However, some babies are not healthy enough to handle the stress and demonstrate an abnormal heart rate pattern. This test is often done if the non-stress test is abnormal. The contractions are a challenge to the baby, similar to the challenge of normal labor.