Contraction Stress Test (CST)

Who Gets the Test?

Some women who have complications during their pregnancy need a CST, although the test is much less common than it once was. More often, you would get a nonstress test or a biophysical profile. If those results indicate a possible problem, your doctor may suggest a CST as a follow-up.

What the Test Does

The contraction stress test helps predict how your baby will do during labor. The test triggers contractions and registers how your baby’s heart reacts. A normal heartbeat is a good sign that your baby will be healthy during labor.

How the Test Is Done

You’ll lie down with two belts around your belly. One measures your baby’s heartbeat and the other measures contractions. To trigger contractions, your doctor may give you a dose of the drug oxytocin through an IV in your arm. Or your doctor may suggest that you rub your nipples through your clothing, which can start contractions. Then you wait while the monitors record contractions and your baby’s heartbeat. The test takes about two hours. The contractions can be uncomfortable.

CST is usually safe, but it sometimes triggers early labor. The test is riskier for women who have placenta previa, a higher risk of uterine rupture, or who had a previous C-section. Your doctor will help you weigh the benefits and risks before the test.