Contraction stress test

If the nonstress test is nonreactive (see the discussion on the opposite page), you may need to take a contraction stress test. A contraction stress test (CST), also called a stress test, evaluates the baby's well-being. It measures the response of the fetal heart to mild uterine contractions that mimic labor.

If you have had a problem pregnancy in the past or experienced medical problems during this pregnancy, your doctor may order this test in the last few weeks of pregnancy. This test may be done every week, beginning around 32 weeks.

In some cases, the doctor may order the nonstress test alone or order both the nonstress test and the contraction stress test. The contraction stress test is considered somewhat more accurate than the nons tress test.

How the Test Is Performed
This test is usually done in the hospital because it can take an hour or more and occasionally triggers labor. A monitor is placed on your abdomen to record the fetal heart rate. In some hospitals, nipple stimulation is used to make the woman's uterus contract. In other hospitals, oxytocin is given intravenously in small amounts to make the uterus contract. Results indicate how well a baby will tolerate contractions and labor.

Test Results
A slowed heart rate after a contraction may be a sign of fetal distress. The baby may not be receiving enough oxygen or may be experiencing another difficulty. The doctor may recommend delivery of the baby. In other cases, the doctor may repeat the test the next day or order a biophysical profile. If the test shows no sign of a slowed fetal heart rate, the test result is reassuring.