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Non-Stress Test (NST)

The Non-stress test (NST) during pregnancy is a painless procedure that takes place during pregnancy as a way to evaluate the baby's current condition as they grow and develop in your womb. The non-stress test typically occurs if the pregnant woman has gone past her due date or is in a high-risk pregnancy.

The non-stress test is given by your doctor or health care professional to determine the health of your unborn baby. During the test the doctor will monitor your baby's heartbeat during a few different stages. First, the heart beat will be monitored while the baby is resting and then another while the baby is moving. The baby's heart rate should increase during the second part of the test while he or she is moving and kicking. There are a couple different things that can occur during pregnancy that might make a doctor or health care professional interested in doing a non-stress test during pregnancy.

Reasons For a Non-Stress Test During Pregnancy:

Mothers with diabetes that is treated with insulin often are considered high risk and have conditions like high blood pressure are often required to get a non-stress test during pregnancy. Mothers who end up with gestational diabetes also typically get the non-stress test for the same reason. Gestational hypertension is another reason some mothers are encouraged to get the non-stress test later in pregnancy to ensure the baby is okay. For mothers who have had ultrasounds where the baby does not appear to be developing or growing properly also get the stress test to help determine if the baby is okay or not. If there is too much or not enough amniotic fluid in the amniotic sac, the mother is required to get a non-stress test to rule out if it is because something is wrong with the development of the baby. 

Certain pregnant mothers also have to have certain procedures done during pregnancy that are often followed up by a non-stress test to ensure the baby is still doing alright. These procedures include the external cephalic version, which can be performed to turn a breech baby prior to delivery. Those who have had amniocentesis also will be encouraged to get a non-stress test done to make sure the baby is progressing normally in spite of the procedure, which can sometimes be considered risky. 

Most often, mothers who go past their due date are encouraged to get a non-stress test to make sure the baby is still moving and thriving. If you've had previous pregnancy loss during the second-half of the pregnancy, you might be encouraged to have a non-stress test done just in case. This might occur around 28 weeks.

Preparing for the Non-Stress Test:

To get prepared for the non-stress test, your doctor or midwife will most likely advise you to eat a meal just before the test is performed to ensure the baby is stimulated and likely to move around more. However, there is no guarantee that this will help, but it might. During the procedure you will lie on your left side and the technician will strap a monitor your your belly to monitor the baby's heartbeat and movement. Another device will also be placed on your belly to help record the contractions that occur in your uterus. If the baby appears to be asleep, the doctor might have you drink a glass of cold water, juice or soda to get him or her awake and moving. You can expect the entire test from start to finish to take about an hour to an hour and a half. 

Non-Stress Test Results:

The result is normal if the results of your baby's non-stress test results come back with a heart rate that is faster (at least 15 beats per minute over the resting rate) while he or she is moving for a 15-second period on two different occasions, during 20 minutes. If the test comes back as nonreactive, this isn't necessarily a bad sign, it just means the non-stress tests were inconclusive. Likely this will mean that if the doctor predicts the baby is no longer doing well in the womb, he or she will likely decide to induce labor. A nonreactive test can indicate that the baby is no longer getting oxygen or that there are problems with the placenta. If either of these are true, it is best to deliver the baby as soon as possible. 

If the results come back normal and are considered to be nothing of concern, your doctor or health care professional might still wish to continue doing a non-stress test each week just to ensure the baby continues to do well until signs of labor begins. 


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