The Non-Stress Test

Posted on: June 21, 2021 | Body, education, Health, Information, Pregnancy, Prenatal

Throughout pregnancy there are tests, screenings, poking and prodding. These many methods of monitoring help provide knowledge into the health and well-being of the growing fetus and the gestational carrier. Stress occurs in everyday hustles and bustles. Stress is a cautionary factor in pregnancy and birth, as stress may cause:high-blood pressures, elevated heart rates (in baby and carrier), birth defects, pre-term labor, for example. Non-stress tests are a common test conducted towards the 2nd to 3rd trimester to help providers gauge the growth, development, and health of both parties. These are particularly induced when there is a situation of a high-risk pregnancy.

What Is A Non-Stress Test

A non-stress test (or NST) is a non-invasive monitoring of a baby’s health while in utero; generally around 28-32 weeks of pregnancy and can be up to delivery. During this monitoring, the gestational carrier is at a state of rest and the movement, heart rate, and the changes in heart rhymes during contractions of baby are being tracked. The NST follows the resting natural fetal heart rate, a heart rate variabilities, accelerations, decelerations, and contractions within the testing period.

How Is It Done

The non-stress test is non-invasive as it has low maternal and fetal risks. The NST includes an electronic fetal doppler attached to the abdomen of the pregnant individual with an elastic band. The fetal monitor records fetal heart rate pattern, contractions, fetal cardiac activity, maternal blood pressure and heart rate on a graph. This is an outpatient procedure, where the gestational carrier is seated in a reclined position and involves 20 minutes to 60 minutes of continuous monitoring. It is important the gestational carrier is at rest, as to get the most accurate reading of results.

Why It May Be Needed

A non-stress test is used for a myriad of different situations, and especially when there may be a compromise in fetal development pregnancy.  NST helps to identify if a fetus is at risk for intrauterine death or neonatal complications. An NST before 32 weeks can vary with false positives, as the fetal heart rate is still at a level of growth. Additionally, an NST before 24 weeks gestation will come up non-reactive. Giving inconclusive results. 

What Is A Non-Stress Test Looking To Detect

Non-stress testing looks to detect stresses or complications that may arise or be present during pregnancy. Because these stresses on the baby, can result in preterm labor or even fetal demise, an NST is one benefit to gaining information on baby’s well-being until the birth. Some implications for an NST candidate may include:

  • High-risk Pregnancies
  • Advanced Maternal Age
  • Fetal growth restriction
  • Diabetes, pre-gestational and gestational diabetes
  • Hypertensive disorder, chronic hypertension, and preeclampsia
  • Decreased fetal movement
  • Post-term pregnancy
  • Multiple pregnancies
  • Recurrent pregnancy loss
  • Medical conditions
  • Cholestasis of pregnancy

The American College of Obstetrics and Gynecologist defines a normal test result, in which two or more accelerations peak at 15 bpm or more above baseline, each lasting 15 seconds or more, and all occurring within 20 minutes of beginning the test. It is important to note that an abnormal stress test is not always ominous and can occur with a sleeping fetus. If a test is not reactive, the fetal heart rate should be monitored for at least 40 minutes to account for the fetus sleep cycle, and vibroacoustic stimulation can be used to stimulate fetal movement. Continuous nonreactive NST can indicate central nervous system depression, but further evaluation is necessary, usually in the form of a biophysical profile or contraction stress test. (Reference)

Non-stress tests are a common occurrence in the third trimester for many pregnancies. What’s important to remember, is that while these tests can be inconvenient weekly appointments, (additional to the routine prenatal appointment) they can also have big calming factors. Knowing that all is well with baby and body. It’s good to ask questions when you are unsure of a procedure, test or screening. It’s your right to! Don’t be afraid to seek out alternative measures if you feel you are not being heard.