Non-Stress Tests Measure Your Baby’s Movements, Heart Rate

A closer look at baby late in your pregnancy
Nicole with baby

A mom-to-be with a high-risk pregnancy cherishes every bit of positive feedback she can get. A non-stress test can tell you more about how your baby is doing in the final weeks of pregnancy.

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Most expectant parents want reassurance that they will deliver a healthy baby. Understandably, a woman who is told her pregnancy is high risk is likely to worry more than someone without pregnancy problems. Even healthy women are sometimes given special tests as a precaution to monitor their baby’s health late in the pregnancy.

“The non-stress test is a special test we like to perform when the mom has a high-risk pregnancy or when she develops problems during her pregnancy,” says maternal fetal medicine specialist Abdelaziz Saleh, MD. “We usually recommend these special tests at 32 or 34 weeks, although sometimes we’ll begin monitoring the baby’s movements as early as 28 weeks.”

Who might need a non-stress test?

According to Dr. Saleh, certain conditions warrant non-stress testing and determine how frequently the tests are done. These health conditions can include:

  • Diabetes and other pre-existing health conditions
  • Problems that arise during pregnancy, such as high blood pressure or gestational hypertension
  • Issues with the baby, such as appearing too small, being diagnosed with a birth defect or being less active than normal
  • Situations where the mom previously lost a baby in the second half of pregnancy

Other instances when doctors might order a non-stress test are:

  • A woman is age 35 or older
  • The pregnancy lasts longer than 42 weeks and they want to check on the baby’s health

What happens during the test?

Non-stress tests – so called because they do not put any stress on the fetus — are used to monitor the baby’s movements. The noninvasive test can take anywhere from 20 to 90 minutes, depending on how active the baby is. Usually, the test is performed in your doctor’s office or at the hospital.

Nicole Herbst, 40, whose pregnancy was not considered high-risk, went every week for non-stress tests beginning in the 34th week of her pregnancy. For the most part, the test took place during Herbst’s prenatal visits.

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“I sat in a recliner with my entire belly exposed,” she says. “The nurse strapped a belt with two circular, flat discs around my abdomen. She gave me a device to click every time I felt my baby move.”

The discs on Herbst’s belly linked to sensors that measured her baby’s heart rate. The heart rate, in turn, was recorded.

“It reminded me of an EKG machine because there was a printout of the baby’s movements,” says Herbst, who was expecting her first child after experiencing difficulty getting pregnant and suffering a miscarriage.

How non-stress tests work

The test looks at the number of movements the baby makes over a 20-minute period. If the baby is sleeping or inactive during the test, the mother drinks cold water or juice to get him moving.

The test outcome is either reactive or nonreactive. A reactive result means the baby’s heart beats faster than her resting rate at least twice during the test. This is considered reassuring. A nonreactive result means her heart rate doesn’t accelerate. In that situation, your doctor may want you to take additional tests to make sure the baby is healthy.

Extra reassurance makes tests worthwhile

Herbst says the extra tests were reassuring.

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“Even though they took more time, I was glad that my OB/GYN followed these extra precautions,” she says. “It gave my husband and me peace of mind.”

In March 2014, the Herbsts welcomed their baby girl, who was born at Fairview Hospital.

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