Important Facts about Third-Trimester Prenatal Testing That You Should Know

August 13, 2018

Third-trimester prenatal testing is ordered by your provider to monitor fetal health or fetal well-being when issues arise.

Why I am here and who I am:

Hey mama, I am Trish— AKA Labor Nurse Mama. I am a labor and delivery nurse with over 15 years of high-risk OB experience. I am also a mama to 7 kids and have given birth to 6. This means I am quite familiar with the postpartum period and how to navigate it. I am the online birth class educator for Calm Labor Confident Birth and The VBAC Lab birth classes and the mama expert inside our Calm Mama Society a pregnancy & postpartum membership community! I am passionate about your birth and motherhood journey! You can find me over on IG teaching over 230k mamas daily. I am passionate about your birth and motherhood journey!

We make a small commission from some of the links (you dont pay any more for using our links); however some of the recommendations, we do not earn anything; we just love em and want you to know about them. Click here for our full disclosure. Thank you!

Today, I admitted a patient whose chart said “ELDERLY”  She was 35!!! What the heck? That's not cool. My coworkers may have called me that but not to my face. Listen, I was high risk with Greyson. First, because I was AMA, CRINGE…..That is not fun to hear. For you young pregnant women, that means Advanced Maternal Age and it sucks. Secondly, because I have MTFHR mutation (or know as the ‘m-f-er' to those of us in this field). You don't have the inside track on high-risk pregnancy, although that also means I know too much. But, I wanted to give you guys a central location with an easy to understand explanation of each third-trimester prenatal test that is done and why your provider might order it.

This will be a short and understandable read, giving you more insight into these tests and their results.

We have included a free PDF download with questions to ask your provider if these tests have been ordered.

EDUCATION IS KEY TO BIRTH! Read Book, take classes, and follow blogs like mine (written by a labor nurse).

Here are a few more blogs written by birth professionals.

A Life in Labor (check out her customizable birth plan).

Pulling Curls, who has an amazing online prenatal class.

Take a Breastfeeding Class from Milksnob and be prepared for all the hardships you encounter as a dedicated breastfeeding momma.

Why would your OB order Third-Trimester Prenatal Testing?

High-risk pregnancy diagnosis: You may have had complications during a previous pregnancy or developed complications during this one. Medical conditions: Diabetes, High Blood Pressure, Heart conditions, Complicated digestive disorders. Advanced Maternal Age: You old (like I was with Greyson) Decreased Fetal Movement (READ THIS!!!!!) If you go past your due date (Post Dates Pregnancy) Pregnant with one than one baby (multiples)

What are the types of third-trimester pregnancy testing?

Fetal Kick Counts:

It is SO IMPORTANT!!! Please read how and start doing this dailyTracking your little one's movement might be the most valuable tool you can utilize in your third trimester. Fetal movement is one of the few indicators that you can use to assess your baby's well-being at home. 

Non-stress test:

(NST) This is probably the most common of the third-trimester pregnancy testing that is ordered. You will be hooked up to a fetal monitor, and your nurse will watch the baby's heart rate to assess the fetal well being. (usually done in triage alongside a BPP) A well-oxygenated fetus moves and responds to stimuli. Decreased fetal movement is a SIGN OF DISTRESS. The fetal heart will indicate whether the baby is okay or needs attention. A reassuring result would show that the baby has 2 or more heart rate accelerations within a twenty minute period.

Forty minutes of no accelerations warrant further testing. Many times, If the baby does not “pass” this test, we will most likely compare to the BPP results and decide whether its time for this baby to come out.

Biophysical Profile:

Both the BPP and NST are common third-trimester prenatal testing that takes place in your hospital on the Labor and Delivery floor. Most of the time your provider will write a prescription/order and send you to triage. Expect to be at the hospital for up to 3 hours (sometimes more). We most always do both tests together. We score the  BPP based on the following components: Fetal Heartrate, Fetal breathing movements, Fetal Body movements, Fetal muscle tone, and amniotic fluid amount with a possibility of 0 or 2 points. Fetal heart rate monitoring: The fetal heart rate is reactive or nonreactive. The baby's heart rate should go up two times or more (even better) times during a 20-minute period, the results are called reactive, and you score 2 points. If it doesn't go up at least twice during a 40-minute period, then it is called nonreactive, and you score 0 points. A sleeping baby may not be reactive. Breathing movements: If your baby has at least one episode of breathing movements for 30 seconds or more in a 30 minutes period, add 2 points to your score. If not, you score 0 points. Fetal movement: If your baby moves his or her body or limbs three times or more within 30 minutes,  add 2 points. If your baby's movements don't meet the criteria, we give no points, and the score is 0 for this category. Fetal muscle tone: For this portion, your baby needs to bend and extend a limb quickly, again add 2 points. If no qualifying movements, we add 0 points.

Amniotic fluid level: The ultrasound tech will look for the most massive pocket of amniotic fluid. The fluid pocket must be a certain size to gain 2 points. If your amniotic fluid level is not high enough, you score 0 points. A perfect score is 10. An ultrasound is performed to do this test. A reassuring score would be 8-10. Consequently, A count of less than four would mean more testing is needed. Scoring a six earns you a repeat BPP within 12-24 hours.

Doppler Ultrasound of the Umbilical Artery:

Doppler ultrasound is used to check the blood flow of the umbilical artery and is usually performed with other testing. A regular flow would indicate proper oxygenation of the fetus. An abnormal result shows a problem with oxygen flow to the baby.

Contraction Stress Test:

CST is the same as an NST except the nurse will most likely start an IV and give you Oxytocin (Pitocin) (one of the many medications we use in Labor and Delivery) to start contractions. Alternatively, Nipple stimulation is another method used to stimulate contractions. We monitor the response of the fetal heart rate related to the contractions. A baby with enough oxygen in their reserve handles contractions without its heart rate decreasing. Decelerations indicate a problem and should be investigated. I hope that understanding the what and the why of third-trimester prenatal testing will assist you and empower you to make informed decisions.

You need to follow us on PINTEREST and INSTAGRAM! Head over to both and click follow!

Finally, post your comments about third-trimester prenatal testing, questions, and experiences here, so we can all learn from one another. We are a tribe!

Just a little Disclaimer: As always, I am just writing my thoughts and what I’ve learned along the way. Although I am in fact a labor and delivery RN, This is not medical advice. You should always seek and follow the advice of your care provider.

This post may contain some affiliate links (which means if you make a purchase after clicking a link I will earn a small commission, but it won’t cost you a penny more)! Thank you! For our full disclosure read here)


Related Articles

Latest Podcast Episodes