A stress test pregnancy is also known as a contraction stress test (CST) . It is a test that measures the fetal heart rate after the mothers uterus is stimulated to contract. The test is done to make sure the fetus can handle contractions during labor and get the oxygen needed from the placenta. During the test, the uterus is stimulated with pitocin, a synthetic form of oxytocin, which brings on mild contractions, letting doctors see the effect of contractions while monitoring the babys heart rate. The test can determine whether the babys heart rate remains stable during contractions. The test is usually done if a nonstress test or biophysical profile indicates a problem. The test can induce labor, so it is only recommended when necessary. The test can be done at 34 weeks or later. The results of a contraction stress test are ready right away.