Welcome to Birthing Balance! Are you a pregnant mama wondering about the special tests, like the non stress test fetal examination, that can be done to check your baby’s well-being in-utero? Look no further! This post has everything you need to know about the biophysical profile and non stress test when pregnant.
What is a Biophysical Profile?
A biophysical profile is most often used with a fetal non stress test and vice versa. Using both of these tests, in addition to an amniotic fluid assessment is known as a modified biophysical profile and is done for the same reasons as a regular biophysical profile.
The amniotic fluid volume is a key part of this test because it gives a good idea on how well the placenta is working. If the results are nonreactive, this could mean the fetus is having trouble getting enough oxygen.
A cardiotocograph (CTG) machine is used to read your contractions and assess fetal wellbeing by examining the pattern of your baby’s heartbeats alongside the size of your contractions.
The biophysical profile generally lasts 30-minutes and uses ultrasound to assess fetal heart rate, fetal breathing movements (practice breathing), fetal tone, amniotic fluid volume, and fetal movements. A scoring system is used when evaluating these 5 areas to determine if your baby is “reactive” or “nonreactive.”
1. Fetal heart rate
Fetal heart rate is tested using a non-stress test. During the non stress test, 2 points are given if it is “reactive”, defined as at least 2 episodes of fetal heart rate accelerations of at least 15 beats per minute and at least 15 seconds of duration from onset to return, associated with fetal movement [4].
2. fetal breathing movements
2 points are added if one or more episodes of rhythmic breathing movements (practice breaths) are observed for 30 or more seconds within a 30-minute observation period [4].
3. Fetal tone
2 points are added if there are one or more episodes of extension of a fetal extremity or the fetal spine are observed with return to flexion (the typical bent position) [4].
4. Amniotic Fluid volume
Additionally, 2 points are given if a single deepest vertical pocket of the amniotic fluid is 2 or more centimeters. Plus, the horizontal dimension should be at least 1 cm [4].
5. fetal movement
2 points are given if three or more discrete body or limb movements are seen within 30 minutes of observation. An episode of active continuous movement is counted as one movement [4].
Biophysical Profile Results:
Zero points are assigned for any criteria not met. But, a score of 10/10 for the non-stress test and biophysical profile, or 8/8 if the non stress test is not done, or 8/10 (including 2 points for amniotic fluid volume) is a normal test result [4].
A score of 6/10 (including +2 points for amniotic fluid volume) is an equivocal result [4].
A score of 6/10 or 8/10 with oligohydramnios (low amniotic fluid volume; 0 points for amniotic fluid testing) is an abnormal test, and further assessment and correlation with the clinical setting are indicated [4].
And a score of 0-4/10 is abnormal; the risk of fetal asphyxia (suffocation) within one week is high if there is no intervention, and delivery is usually indicated [4].
No matter what the score is, if there isn’t enough amniotic fluid measured, more frequent testing is generally advised. Before proceeding with further interventions, ensure you are not dehydrated.
What is a Non Stress Test When Pregnant?
The non stress test is one of the most widely used techniques for evaluating fetal well-being in-utero [1]. If the test is needed it generally starts between 32-34 weeks of pregnancy.
This test includes attaching two “belt-like” monitors on your belly. One is measuring your contractions and the other is measuring fetal heart rate for 20 minutes while assessing the number, amplitude, and duration of accelerations in the heart rate that usually correlate with fetal movement [1].
A non-stress test is intended for the surveillance of high-risk pregnancies when the fetus is judged clinically to be at risk for hypoxemia (low oxygen levels in the blood) or an increased risk of death.
During a non-stress test, it’s expected that your baby’s heart rate will increase when they are moving or responding to a contraction. If the baby’s heart rate decreases during movement or a contraction, this is a sign that baby is not coping well.
The point of the non-stress test is to see baby’s “reactivity” and the test will either come down to a “reactive” diagnosis or “nonreactive.” If the results tests are non-reassuring, sometimes they will be repeated weekly or done twice a week.
“Non-reassuring fetal status is not an adverse event per se, but rather an indicator of an underlying condition resulting in temporary or permanent oxygen deprivation to the fetus which may lead to fetal hypoxia and metabolic acidosis” [5].
When Might You Need a Biophysical Profile or Non Stress Test When Pregnant?
Indications for a non-stress test (often paired with a biophysical profile) include maternal conditions of:
- Gestational hypertension (high blood pressure in pregnancy)
- If you fall or get into an accident
- Gestational diabetes mellitus (GDM; pre-gestational or GDM that developed during pregnancy that is uncontrolled or medically treated)
- Systemic lupus erythematosus
- Chronic renal disease
- Antiphospholipid syndrome
- Hyperthyroidism (uncontrolled)
- Hemoglobinopathies (sickle cell, sick cell- hemoglobin C, or sickle cell- thalassemia disease)
- Cyanotic heart disease
- Rh sensitization
- Or, if you had any of these complications in your last pregnancy
More pregnancy-related conditions that indicate a non-stress test include:
- Baby seems to be small, raising the question of intrauterine growth restriction (IUGR)
- Noticed decrease in fetal movement (Check out how to use kick counting during pregnancy here!)
- Oligohydramnios (low amniotic fluid volume)
- Going past your “guess date” (after 40 weeks of pregnancy)
- Isoimmunization
- Previous fetal demise (unexplained or recurrent risk)
- Monochorionic multiple gestation (with significant growth discrepancy)
“The prenatal non stress test has utility in isolation in post-term pregnancies and patients with decreased fetal movement. When the non-stress test is not reactive, the testing period should extend another 20 minutes in an attempt to delineate between the fetus in a period of prolonged quiet sleep from those who are hypoxemic or asphyxiated. Vibroacoustic stimulation (VAS) may be used to change fetal state from quiet to active sleep and shorten the length of the NST. If the NST remains nonreactive after 60 minutes, the fetus should undergo evaluation with an ultrasound biophysical profile” [1].
ACOG Says a Biophysical Profile and Non Stress Test When Pregnant Are Indicated When…
The American College of Obstetrics and Gynecology is not the most reliable source for pregnancy or birth information. I find much more value and truth looking at high-quality research studies. This is because the final decision on what is put on ACOG is up to the ACOG committee opinion.
Still, ACOG makes the guidelines that OB-GYNs are expected to abide by in their maternal health practices, and that is what makes looking at ACOG interesting.
In this case, ACOG’s guidelines are cohesive with the other research found on when a non stress test and/or biophysical profile are indicated.
ACOG states, “Special testing during pregnancy most often is done when there is an increased risk of pregnancy complications or stillbirth. This can occur in the following situations:
- High-risk pregnancy (a woman has had complications in a previous pregnancy or has a pre-existing health condition such as diabetes mellitus or heart disease)
- Problems during pregnancy, such as fetal growth problems, Rh sensitization, or high blood pressure
- Decreased movement of the fetus
- Pregnancy that goes past 42 weeks (post-term pregnancy)
- Multiple pregnancy with certain complications” [6]
Do These Tests Work?
Non-stress tests and modified biophysical profiles can reassure you that your baby is healthy and getting enough oxygen at the time of the tests.
In high-risk pregnancies, these tests can be impactful tools to make decisions about how to best proceed with your pregnancy and options for care.
Questions or Comments?
If you have any questions or comments, please leave them below👇🏻
Talk soon, mama!
– Katelyn Lauren
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References:
[1] Umana OD, Siccardi MA. Prenatal Non-stress Test. [Updated 2022 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537123/
[2] Preboth M. ACOG guidelines on antepartum fetal surveillance. American College of Obstetricians and Gynecologists. Am Fam Physician. 2000 Sep 01;62(5):1184, 1187-8. [PubMed]
[3] UpToDate: Nonstress test and contraction stress test
[4] UpToDate: Criteria for the biophysical profile test
[5] Gravett, C., Eckert, L. O., Gravett, M. G., Dudley, D. J., Stringer, E. M., Mujobu, T. B., Lyabis, O., Kochhar, S., Swamy, G. K., & Brighton Collaboration Non-reassuring fetal status Working Group (2016). Non-reassuring fetal status: Case definition & guidelines for data collection, analysis, and presentation of immunization safety data. Vaccine, 34(49), 6084–6092. https://doi.org/10.1016/j.vaccine.2016.03.043
[6] ACOG: Special Tests for Monitoring Fetal Well-Being
DISCLAIMER: This post is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding you or your baby’s health. Please read my Medical Disclaimer for more info
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