What Prenatal Tests are Done in the Third Trimester? By Dr Prerna Jhawar

4 min read

Reviewed by Dr. Prerna MBBS, MS(Obstetrics and Gynaecology),
FFM Consultant, Fetal Medicine,
Rainbow Children's Hospitals, Bengaluru

Dr. Prerna

Dr Prerna Jhawar is a Fetal medicine expert with 12+ years of experience. As a Fetal medicine expert, Dr Prerna takes care of babies while they are still in their Mother’s womb! Sharing the More

Written by Ambili Kartha

Ambili Kartha

Ambili Kartha is engaged in content creation and editing for more than 6 years and has the additional experience of being the mother of two children. She is part of content team.

Prenatal tests in third Trimester

As your delivery date approaches, the number of your routine check-up will increase. Your doctor will check your blood pressure and sugar levels on every visit. Urine tests and ultrasound tests are also an integral part of third-trimester prenatal tests. This period of pregnancy is crucial, and you must be prepared for any obstacles like gestational diabetes or preeclampsia. So, what prenatal tests are done in the third trimester? And why are they important?

All the prenatal tests during the third trimester are important and will reveal some valuable information about your growing baby. You can see your baby’s movements or even your baby’s smile during an ultrasound. It is magical to experience such a thing for the first time. Other prenatal tests will help you determine whether you should go for normal delivery or a c-section. Here is a detailed list of third-trimester prenatal tests for you.

In This Article

List of Important Prenatal Tests Done in the Third Trimester

Your third trimester prenatal tests will involve a lot of routine blood and urine tests. Your doctor will check if you are maintaining the right levels of blood counts, whether you are at risk of urinary tract infection, whether your blood sugar and blood pressure levels are under control, etc.

Let us now take a look at some of the routine third trimester prenatal tests.

1. Urine Tests

urine test

Your doctor will prescribe your urine test for the following assessments:

a) Urine Glucose Levels

Gestational diabetes is one of the common pregnancy complications. Urine tests are routinely prescribed by doctors to check for blood sugar levels. If sugar levels are more than normal, then it suggests gestational diabetes. The Human Chorionic Gonadotropin hormone or HCG hormone releases from the placenta only during pregnancy. This HCG hormone is vital for a healthy pregnancy, but can decrease the level of insulin in your body. This decreased insulin, sometimes causes diabetes in some pregnant women.

[Read: HCG Levels Chart during Pregnancy]

b) Assessment of Protein

Our bodies generally do not let go of the necessary protein. But in certain conditions like diabetes, high blood pressure, and kidney failure or, proteinuria, protein can be found in large quantities in the urine. This assessment of urine for protein is necessary right before delivery. High protein in the urine along with high blood pressure is a sign of preeclampsia.

c) Urine Culture

The presence of any harmful micro-organisms in the vaginal tract may not harm the mother much, but it can get fatal for the fetus. As a newborn baby’s immune system is still developing, vaginal delivery can put the baby exposed to infection. So, it is better to do a urine culture and take antibiotic treatment if necessary.

[Read: Urine Test And Urine Culture During Pregnancy]

2. Blood Test

blood test

The routine blood tests during the third trimester of your pregnancy include:

a) CBC Test

Many women suffer from anemia during pregnancy. It is important to check the hemoglobin levels and red blood cell count in the blood. Besides, a rise in the white blood cells indicates an infection. Your gynecologist can recommend a complete blood picture or CBC test to check the levels of various blood components like RBCs, WBCs, and platelets.

b) Glucose tolerance test

Many women may suffer from gestational diabetes, which is evident in the third trimester. This may lead to a big baby or polyhydraminos which can further complicate the pregnancy. So the doctor will order this test to rule out diabetes.

3. Electronic Fetal Heart Rate Monitoring

Fetal Heart Rate Monitoring

As you approach your delivery date, the baby inside you starts growing rapidly. During the last four weeks of pregnancy, the baby can gain an additional two pounds. This gain in size gives them little space to move and breathe. Doctors often check the fetal heart rate during the last few weeks of pregnancy, during labor, and delivery. The fetal heart rate monitoring ensures whether the baby is doing well inside or not.

[Read: Electronic Fetal Monitoring During Labor and Delivery]

4. Ultrasound Scan

ultrasound -Prenatal tests in third Trimester

You must do an ultrasound test before going for the last check-up with the doctor before delivery. This ultrasound can tell you the position of the baby, the position of the placenta, the levels of amniotic fluid, and the proper growth of the baby. This will help you decide whether you should go for normal childbirth or a C-section delivery.

So, each of these third-trimester prenatal tests has its separate importance and you should not ideally overlook them. But you should always know why each test is necessary and what are the risk factors from your doctor.


1. What Are the Three Most Common Prenatal Tests For Diagnosing Birth Defects?

There are multiple tests to identify a genetic disorder or birth defect. Out of them ultrasound scans, CVS, AFP test, and amniocentesis are the most common.

2. When Do You Have an Ultrasound in The Third Trimester?

Your doctor will likely suggest you two ultrasound tests during your third trimester. One at the beginning approximately at 28 weeks and one towards the end of 36 weeks.

3. How do You Know if Something is Wrong in Your Third Trimester?

If there is continuous abdominal pain and contraction more than 4 times in one hour before 36 months then it is a cause of concern.

Read Also: Pregnancy Foods And Exercises For Third Trimester

Ambili Kartha,B. Sc Zoology (St Xavier’s college for women)

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