A contraction stress test checks to see if
your unborn baby (fetus) will stay healthy during the
reduced oxygen levels that normally occur during contractions when you are in
labor. This test includes
external fetal heart monitoring . The test is done when you are
34 or more weeks pregnant.
During a uterine contraction, the
blood and oxygen supply to your baby drops for a short time. This is not a
problem for most babies. But the heart rate of some babies gets slower. This
change in heart rate can be seen on the external fetal monitoring
For a contraction stress test, the hormone oxytocin is
given to you in a vein (intravenously, or IV) to cause labor
contractions. You may also massage your nipples. This tells your body to
release oxytocin. If your baby's heart rate slows down (decelerates) in a
certain pattern after a contraction instead of speeding up (accelerating), your
baby may have problems with the stress of normal labor.
contraction stress test is usually done if you have an abnormal nonstress test or
biophysical profile. A biophysical profile uses
ultrasound during a nonstress test to measure a series
of physical characteristics of your baby. You may have more than one contraction stress test during your
Some doctors may do a biophysical profile or a
Doppler ultrasound test instead of a contraction
Why It Is Done
A contraction stress test is done to
- If your baby will stay healthy during the
reduced oxygen levels that normally occur during contractions during
- If the
placenta is healthy and can support your baby.
A contraction stress test may be done when results from a
nonstress test or a biophysical profile are not in the normal range.
How To Prepare
You may be asked to not eat or drink
for 4 to 8 hours before the test. Empty your bladder before the test.
If you smoke, stop for 2 hours before the test because smoking can lower
your baby's activity and heart rate.
You will be asked to sign a
consent form before a contraction stress test. Talk to your doctor about any
concerns you have regarding the need for the test, its risks, how it will be
done, or what the results will mean. To help you understand the importance of
this test, fill out the
medical test information form(What is a PDF document?).
How It Is Done
A contraction stress test may be done
in your doctor's office or hospital by a
family medicine doctor or an
obstetrician and a trained laboratory technician or
nurse. You usually do not 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 so you will not have 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
uterine 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 for 10 minutes. Your blood pressure and other vital signs are also