Non-Stress Test

A. What it is

The test, sometimes called a cardiotocography, records your little one's movement, heartbeat, and/or your contractions.

A nonstress test is a common prenatal test used to check on your baby's health. During a test, your little one's heart rate is monitored to see how it responds to baby's movements or during contractions if your in labor. The term "nonstress" refers to the fact that nothing is done to place stress on your little one during the test and can reassure you and your team that your little one is healthy and getting enough oxygen.

Typically, a nonstress test is recommended when it's believed that the your little one is at an increased risk of death. A nonstress test may be done after 26 to 28 weeks of pregnancy. Certain nonstress test results might indicate that you and your little one need further monitoring, testing or special care.

A nonstress test is a noninvasive test that doesn't pose any physical risks and doesn't bother your little one or to you.

B. How it is done

During the nonstress test, you'll lie on a reclining chair either in your practitioner's office or a hospital. You'll have your blood pressure taken at regular intervals during the test.

-Elastic belts with two sensors are placed on the woman's belly. The sensors are connected to an electronic monitoring machine.

-One sensor monitors your little one's heart rate.

-The other sensor is a pressure gauge, which measures the duration of tightening (contractions) of your uterus, if they occur.

-The woman pushes a button on the machine every time she feels the little one move.

-The little one's heart rate is compared during movement and during contractions. Normally, the little one's heart rate increases when the baby moves. But the heart rate may not increase during the testing period.

Your health care provider or a member of your health care team will place a sensor around your abdomen that measures the fetal heart rate and/or contractions.

Typically, a nonstress test lasts 20 minutes. However, if your baby is inactive or asleep, you might need to extend the test for another 20 minutes — with the expectation that your little one will become active — to ensure accurate results. Your health care provider might try to stimulate your little one by placing a noise-making device on your abdomen.

C. Why it may be needed

A nonstress test is used to evaluate a baby's health before birth. The goal of a nonstress test is to provide useful information about your little one's oxygen supply by checking his or her heart rate and how it responds to your little one's movements. The test might indicate the need for further monitoring, testing or delivery.

Normally, your little one's heart beats faster when he or she is active later in pregnancy. normally your little one's heart rate ranges from 100-160 beats per minute and will usually speed up after your little one has moved, if the rate is faster or slower than this range or does not speed up after moving it may mean the little one is not doing well. However, conditions such as fetal hypoxia — when the baby doesn't get enough oxygen — can disrupt this response.

Your health care provider might recommend a nonstress test if you have:

• A multiple pregnancy with certain complications

• An underlying medical condition, such as type 1 diabetes, heart disease or high blood pressure during pregnancy

• A pregnancy that has extended two weeks past your due date (post-term pregnancy)

• A history of complications in a previous pregnancy

• A baby who has decreased fetal movements or possible fetal growth problems

• Rh (rhesus) sensitization — a potentially serious condition that can occur, typically during a second or subsequent pregnancy, when your red cell antigen blood group is Rh negative and your baby's blood group is Rh positive.

• Low amniotic fluid (oligohydramnios)

Your health care provider might recommend having nonstress tests once or twice a week — and occasionally daily — depending on your health and your baby's health.

D. What it is looking to detect

The primary goal of the test is to measure the heart rate of your little one in response to its own movements. Healthy babies will respond with an increased heart rate during times of movement, and the heart rate will decrease at rest. The concept behind a non-stress test is that adequate oxygen is required for fetal activity and heart rate to be within normal ranges.

When oxygen levels are low, the little one may not respond normally. Low oxygen levels can often be caused by problems with the placenta or umbilical cord.

Reactive (normal) result.

If your baby's heart beats faster (at least 15 beats per minute over his resting rate) for at least 15 seconds on two separate occasions during a 20-minute span, the result is normal, or "reactive." Some providers will refer to this as 15x15. (If you are before 32 weeks of your pregnancy, the goal is 10 beats above baseline for 10 seconds. Providers may refer to this as 10x10.)

A normal NST result is reassuring and means that your baby is probably doing fine for now. Your practitioner may want to repeat the test every week (or more often) until your baby's born.

Nonreactive result.

If your baby's heart doesn't beat faster on two occasions as described above, the result is "nonreactive." A nonreactive result doesn't necessarily mean something is wrong. It just means that the test didn't provide enough information and you may need to take it again in an hour.

A reactive non-stress result indicates that blood flow (and oxygen) to the little one is adequate. A nonreactive non-stress result requires additional testing to determine whether the result is truly due to poor oxygenation, or whether there are other reasons for fetal non-reactivity (i.e. sleep patterns, certain maternal prescription or nonprescription drugs).