Contraction Stress Test

Why It Is Done

A contraction stress test is done to:

• Find out if your baby will stay healthy during labor, when contractions reduce the oxygen levels.
• Check to see if the placenta is healthy and can support your baby.

This test may be done when results from a nonstress test or a biophysical profile are not normal.

How To Prepare

Empty your bladder before the test.

If you smoke, stop for 2 hours before the test. Smoking can lower your baby's activity and heart rate.

You may be asked to sign a consent form that says you understand the risks of the test and agree to have it done.

How It Is Done

A contraction stress test may be done in your doctor's office or a hospital. It is done by a family medicine doctor or an obstetrician and a trained lab technician or nurse. You probably won't need to stay overnight.

During the test, you will lie on a bed with your back raised. You will be tilted a little to your left side. This is so you will not put pressure on the blood vessels in your belly. Two belts with sensors will be placed around your belly. One belt holds the sensor that records your baby's heart rate. The other sensor measures your contractions. Gel may be used on your skin with the heart rate sensors. The sensors are hooked to a recording unit. The heart rate monitor may be moved if your baby changes position.

Your baby's heart rate and your contractions are recorded. Your blood pressure and other vital signs are also recorded.

You may be given the hormone oxytocin in a vein (intravenously, or I.V.). It is started at a low dose. The dose is increased until you have three contractions within 10 minutes that each last longer than 45 seconds. Or you may be asked to massage one of your nipples by hand to start contractions. If you don't have a second contraction within 2 minutes of the first, you will rub your nipple again. If contractions do not occur within 15 minutes, you will massage both nipples.

After the test, you will be watched until your contractions stop or slow down to what they were before the test.

How long the test takes

A contraction stress test may take 2 hours.

How It Feels

You may have some discomfort during the contractions. And the belts that hold the sensors in place may feel tight on your belly. Most people say this test is uncomfortable but not painful.

Risks

Electronic fetal monitoring may show that your baby is having problems when your baby is healthy. It can't find every type of problem, such as a birth defect.

Using oxytocin also has risks.

• It may cause labor to start sooner than your expected delivery date.
• It may cause contractions that go on for a long time. This may cause problems with your baby. The contractions usually stop when the oxytocin is stopped. You may get a medicine to stop the contractions. In very rare cases, the contractions don't stop. If that happens, your doctor may suggest delivery.

Results

Results of the test help predict if your baby will stay healthy during labor for the upcoming week. The test may need to be done more than once during your pregnancy.

A contraction stress test may show that your baby's heart rate slows down (decelerates) when your baby is not actually having problems. This is called a false-positive result.