Your Guide to Prenatal Testing for High-Risk Pregnancy

From that first “plus” sign to the day you deliver, pregnancy can feel like one long string of tests. This is especially true if you’ve been diagnosed with a high-risk pregnancy, which often comes with more appointments, closer monitoring and more tests.

In this blog post, we’ll highlight some of the most common prenatal tests for high-risk pregnancies. We’ll make our way through your pregnancy from preconception to the third trimester and offer guidance on when and why each test might be ordered — and what specific conditions they can help detect. 

Remember, this list isn’t meant to be exhaustive. The exact tests your doctor recommends will depend on the unique circumstances and diagnoses.

Preconception Testing

A high-risk pregnancy diagnosis can be applied even before conception takes place. 

Women may be deemed at risk if they’re over the age of 35 (advanced maternal age); have certain genetic conditions; or suffer from conditions such as chronic high blood pressure, diabetes, autoimmune disorders, kidney or heart problems, blood disorders like sickle cell disease, sexually transmitted infections or obesity. 

If you’re thinking about becoming pregnant or trying to conceive, your doctor may order one or more of the following tests. If you become pregnant unexpectedly, these tests may be performed during early pregnancy. 

Genetic carrier screening, which can also be done in the first trimester of your pregnancy, determines whether you carry a gene for certain types of genetic disorders like cystic fibrosis, spinal muscular atrophy, fragile-x syndrome and more. The tester will take a sample of blood, saliva, or tissue from the inside of the cheek. If the results are negative, you do not have the gene for the tested disorder. If you are positive, it means you’re a carrier of that gene. Your doctor may recommend that you meet with a genetic counselor to discuss your options.  

Infectious disease and chronic illness screening is important to rule out or monitor diseases that can be passed on to your fetus. The tester will collect blood to screen for infectious diseases like HIV and other STIs, Hepatitis B and C, or tuberculosis.¹ Your doctor will also evaluate or monitor chronic conditions such as thyroid disease, diabetes or autoimmune conditions that could impact your pregnancy or your chances of becoming pregnant.² 

First Trimester Tests (Conception to 12 Weeks) 

Routine lab tests. You can expect a full slate of lab tests during your first office visit and whenever your doctor deems them necessary throughout your pregnancy. These routine tests include a complete blood count (CBC) and urinalysis. 

You will also receive a blood type test that includes testing for a protein on red blood cells called the Rh factor. If you have it and your fetus does not, it can cause your immune system to attack the fetus’s red blood cells, leading to complications in pregnancy.³

Nuchal translucency (NT) screening (11 to 13 weeks) is conducted via ultrasound and evaluates the amount of fluid at the back of your fetus’ neck — an area called the nuchal fold. If there is too much fluid, it can be a sign of a congenital condition like Down syndrome (trisomy 21), Patau syndrome (trisomy 13) or Edwards syndrome (trisomy 18). Elevated nuchal fluid could also mean a higher risk for congenital heart defects.⁴

Chorionic villi sampling (10 to 13 weeks) tests for genetic problems or chromosomal abnormalities. Your doctor will insert a catheter into your uterus to retrieve a sample of placental tissue.⁵ 

Fetal echocardiogram (as early as 11 weeks) is a specialized ultrasound that can detect issues with your baby’s developing heart. Your doctor may recommend a fetal echo in the first trimester if your baby is at risk for developing heart disease.⁶ 

Second Trimester Tests (13 Weeks to 27 Weeks)

Amniocentesis (15 to 20 weeks). During an amniocentesis test, fluid is taken from around the baby in the uterus to check for genetic disorders or other issues. A needle is used to draw the fluid, guided by ultrasound.⁷

Alpha-fetoprotein test (16-22 weeks) is a blood test that measures alpha-fetoprotein (AFP) levels in your blood to screen for potential birth defects or abnormalities in the baby. It’s done if there are concerns from an exam, symptoms or a high-risk pregnancy.⁸

Cordocentesis (18 weeks or later). A thin needle is inserted through the abdomen and uterine walls to the umbilical cord to retrieve a small sample of fetal blood to test for genetic abnormalities, fetal blood oxygen level, infection or blood disorders. Your doctor may recommend cordocentesis if other diagnostic tests aren’t possible or have failed.⁹ 

Level II ultrasound (18 to 20 weeks) is a non-invasive prenatal screening test that is common in low- and high-risk pregnancies. It’s an effective way to screen for fetal health, fluid levels, fetal movement and heartbeat. If your high-risk pregnancy care team needs to get a closer look or see a different perspective, they may also recommend an MRI.¹⁰ 

Middle cerebral artery Doppler (20 weeks or later) checks for fetal distress, anemia or low oxygen levels. It measures peak blood flow in the artery. If anemia is found, a fetal blood sample may be needed.¹¹

Glucose screening (24-28 weeks) is a blood test to screen for gestational diabetes. If the results of your first test come back in the abnormal range, you may need a follow up.¹²

Third Trimester Tests (28 Weeks to 40 Weeks)

Umbilical Doppler studies (second or third trimester) use non-invasive technology to measure blood flow in the uterus, umbilical artery and baby’s heart. This test helps detect issues like intrauterine growth restriction or twin-to-twin transfusion syndrome.¹³

Biophysical profile (after 28 weeks) includes an ultrasound and a non-stress test (NST) to check your baby’s health. It’s done if there are concerns from an exam, symptoms or a high-risk pregnancy. 

Group B strep (35-38 weeks). Most women are tested for GBS late in their pregnancy. If the vaginal swab test comes back positive for GBS, intravenous antibiotics will be recommended during labor.¹⁴ 

The Right Tests for Your Pregnancy

Remember, each pregnancy is unique. You may not require all of the prenatal tests listed here, or your care team may recommend some that are not outlined above. If you have questions or concerns about any of the many prenatal tests you’ll undergo throughout your pregnancy, be sure to raise them with your care team. It’s important for you to be well-informed and comfortable from that first plus sign all the way to delivery day. 

¹https://www.cdc.gov/nchhstp/pregnancy/screening/index.html

²https://www.marchofdimes.org/find-support/topics/planning-baby/chronic-health-conditions-and-pregnancy#:~:text=Chronic%20health%20conditions%20can%20increase,Preterm%20birth.

³https://www.acog.org/womens-health/faqs/the-rh-factor-how-it-can-affect-your-pregnancy#:~:text=The%20Rh%20factor%20is%20a,refers%20to%20your%20Rh%20status.

https://my.clevelandclinic.org/health/diagnostics/23333-nuchal-translucency

https://fetalcaredallas.com/our-services/diagnostic-testing/chorionic-villi-sampling/

https://www.hopkinsmedicine.org/gynecology-obstetrics/specialty-areas/fetal-therapy/fetal-interventions-procedures/first-trimester-fetal-echocardiography#:~:text=Traditional%20fetal%20echo%20is%20performed,the%20size%20of%20a%20pea.

https://fetalcaredallas.com/our-services/diagnostic-testing/amniocentesis/

⁸https://my.clevelandclinic.org/health/diagnostics/24301-alpha-fetoprotein-test

 https://fetalcaredallas.com/our-services/diagnostic-testing/umbilical-blood-sampling/ https://www.stanfordchildrens.org/en/topic/default?id=fetal-blood-sampling-90-P02447

¹⁰https://fetalcaredallas.com/our-services/diagnostic-testing/level-ii-ultrasound/

¹¹https://fetalcaredallas.com/our-services/diagnostic-testing/middle-cerebral-artery-doppler/

¹²https://www.mountsinai.org/health-library/tests/glucose-screening-tests-during-pregnancy#:~:text=Why%20the%20Test%20is%20Performed,a%20high%20risk%20for%20diabetes.

¹³https://fetalcaredallas.com/our-services/diagnostic-testing/umbilical-doppler-studies/

¹⁴https://www.acog.org/womens-health/faqs/group-b-strep-and-pregnancy

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