Contraction Stress Test (CST) With Twins

Who Gets the Test?

Doctors occasionally use a CST to check on a baby who is showing signs of distress. However, CSTs are very uncommon in women with twins, since the test itself can trigger early labor.

What the Test Does

The contraction stress test helps predict how babies will do during labor. The test triggers contractions and registers how your babies' hearts react. A normal heartbeat is a good sign that a baby will be healthy during birth.

How the Test Is Done

You'll lie down with three belts around your belly. Two to measure each of your babies' heartbeats 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 your rub your nipples through your clothing, which can also start contractions. Then you wait while the monitors record contractions and your babies' heartbeats. The test takes about two hours. The contractions can be uncomfortable.

CST can be risky if you're having twins. It can trigger early labor. Also, 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.

What to Know About Test Results

If your babies' heart rates drop during contractions, it could be a sign of problems. Your doctor may suggest further testing. Sometimes, early delivery is the best option.

If your babies' heart rates stay normal during the test, that's an excellent sign. Still, your doctor may suggest that you take the test again later if other test results show a possible problem.

CST is better at ruling out problems than diagnosing them. Many women with abnormal results have perfectly healthy babies.

How Often the Test Is Done During Your Pregnancy

Women might get a contraction stress test at 32 weeks or later. Before that the test may not be safe. The number of times you need the test depends on your situation. Ask your doctor.

Other Names for This Test

Oxytocin challenge test, stress test

Tests Similar to This One

Nonstress test, biophysical profile

WebMD Medical Reference Reviewed by Traci C. Johnson, MD on January 15, 2019



Pagana KD, Pagana TJ. Mosby’s Diagnostic and Laboratory Test Reference, 10th ed. Mosby: 2010.

ACOG: "Special Tests for Monitoring Fetal Health."

Johns Hopkins Manual of Gynecology and Obstetrics, 4th Edition. Lippincott Williams & Williams, 2010.

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