Genetic Testing During Pregnancy

So much is happening inside your body during pregnancy. You might wonder what your baby will look like or what stage of development they are in. Most pressing of all, you may question if everything is OK in there.

Genetic testing allows parents (and doctors) to get a glimpse into the development of your baby. It also helps determine any genetic issues that need attention during or after your pregnancy. Here’s what you need to know about these tests, what the different types are, and when they’re usually performed.

After the initial excitement of seeing your positive pregnancy test fades, you’ll need to make your first prenatal appointment. Throughout the next 9 months, your doctor will offer various tests that evaluate your health and your baby’s health.

Some tests are intended to look for genetic or other health issues your baby may have. The idea is that, with this information, you can get proper medical care and feel informed about your child’s potential health complications.

Some tests are suggested for everyone during pregnancy. Others may be based on other factors, like your age, ethnicity, or family medical history. That said, genetic screenings or tests are optional during pregnancy.

There are two classifications of prenatal genetic testing. The key difference between the two is that one type assesses the possibility of issues while the other collects more detailed, definitive information for diagnosis.

Screening

Screening tests are generally noninvasive — for example, blood tests or ultrasound — and provide results that may indicate a baby has the potential for certain health issues or birth defects.

These tests do not provide a diagnosis or confirm a diagnosis. In fact, screening tests may show there’s a potential issue when there really isn’t. Alternatively, screening tests may miss issues that are actually there.

Diagnostic

Diagnostic tests are generally more invasive — for example, collecting pieces of the placenta — and can provide definitive results about health issues or birth defects.

Diagnostic tests are often offered to women over age 35, those with a history of birth defects, or those with certain health issues, like diabetes, lupus, or high blood pressure.

Screening tests usually give a positive or negative result with regard to certain conditions or birth defects. They indicate the potential for issues versus a confirmation of diagnosis.

Screenings may be performed in the first or second trimester.

First trimester genetic screening tests

The following screening tests are performed together sometime between weeks 11 and 13 in pregnancy.

  • Maternal blood screen: These blood tests screen for levels of human chorionic gonadotropin (hCG) and pregnancy-associated plasma protein-A (PAPP-A). Very low or very high levels of these proteins may indicate that a baby has a chromosomal disorder.
  • Ultrasound: This imaging test — also referred to as the nuchal translucency (NT) scan — is performed by either placing a probe over the lower abdomen (abdominal ultrasound) or inserting it into the vagina (transvaginal ultrasound). It takes pictures of the developing baby and looks for fluid behind the baby’s neck. If there is excess fluid, it may indicate that the baby has a chromosomal issue or congenital heart defect.

Second trimester genetic screening tests

  • Maternal serum screen: This screening involves a blood test that looks for markers of trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), or neural tube defects. For the most accurate results, this test should be given between weeks 15 and 17, but it can be done anywhere between 14 weeks and 20 weeks, 6 days.
  • Anomaly ultrasound: This ultrasound looks at your baby from head to toe. Your healthcare professional will look at the size of your baby’s head and for other potential physical issues. This ultrasound is usually performed between weeks 18 and 20 and, yes, it’s also the scan where you may find out your baby’s sex.

Combined first and second trimester screening

Instead of taking the results from just one screening, your doctor may suggest gathering a combination of results from a first trimester and second trimester screening. Combining the information from these screenings can offer you a more accurate result than using one screening alone.

Other genetic screening tests

  • Cell-free DNA genetic screening tests: Also called noninvasive prenatal testing (NIPT), cell-free DNA genetic screening tests involve a simple maternal blood test that looks for genetic information from the baby’s genetic material circulating in the mother’s blood. This screening can look for Down syndrome, Patau syndrome, Edwards syndrome, and issues with sex chromosomes. It can also show the baby’s sex. Cell-free DNA screenings can be performed after week 10 of pregnancy.
  • Carrier testing: Another screening can be done before you even get pregnant. This is called carrier testing and it is intended for couples who have concerns about certain genetic inherited disorders they may have in their families. This testing can be done at any time before pregnancy and is usually performed by taking blood or a tissue sample from the cheek.

Genetic tests in pregnancy involve testing the cells from the placenta or chorionic villi. There are various technologies used when testing these materials, including:

  • Karyotyping: Karyotyping involves arranging chromosomes from largest to smallest. This way, any missing, extra, or damaged chromosomes are more easily sorted. Results take between 1 to 2 weeks.
  • Fluorescence in situ hybridization: Also called FISH, this method involves detecting missing/extra chromosomes for trisomy 13, 18, and 21 as well as the X and Y chromosomes. Results take just 1 to 2 days.
  • Chromosome microarray analysis: This method looks for missing/extra chromosomes throughout sets of chromosomes. It may detect issues that karyotyping misses and takes about 1 week to complete.
  • DNA testing: You may also request specific DNA testing if you or your partner have a family medical history of certain conditions, like cystic fibrosis or other genetically inherited health issues.
  • Amniocentesis: Amniocentesis is performed sometime between weeks 15 and 20 of pregnancy. However, your doctor may suggest this diagnostic test anytime before birth depending on the circumstances. To perform the test, your doctor inserts a thin needle into the uterus to collect a small amount of amniotic fluid for analysis. The needle is guided using ultrasound technology for safety. Risks after this test include bleeding or amniotic fluid loss, which both typically resolve on their own. There is a small risk of pregnancy loss with amniocentesis.
  • Chorionic villus sampling (CVS): Chorionic villus sampling involves taking a sample of the placenta (a biopsy) for testing. The collection of tissue may be performed either through the cervix (transcervical) or abdomen (transabdominal). This test is performed earlier in pregnancy than amniocentesis — between 10 and 13 weeks gestation. As with amniocentesis, there is a risk of miscarriage with a CVS. Other risks include bleeding, rupture of membranes, or infection.

While most results may come back as “normal” or negative, this does not always mean that the baby has zero chances of having a genetic disorder.

Again, any result you get from a screening test is not a black and white or “yes”/”no” answer as to whether or not your child will have a certain condition or birth defect. Instead, screenings reveal the potential for certain conditions and birth defects. Positive screening tests are confirmed (or can be confirmed) with further testing.

A positive result on a diagnostic test means your baby has a higher risk of having whatever genetic issue or birth defect the test was looking for. If this happens, your doctor will discuss the different options available as well as any additional care you may need during and after your pregnancy. Your doctor may also refer you to a specialist for more information about the specific disorder.

Can you refuse genetic testing while pregnant?

Genetic testing is optional.

It is your decision whether or not you want to receive genetic testing during your pregnancy. Speak with your doctor about the benefits versus risks of testing. Your doctor can help you make an informed decision that is best for you and your baby. That said, your doctor cannot perform genetic testing without your consent.

Can you find out your baby’s sex through genetic testing?

Yes. You may be able to learn the sex of your baby through genetic testing. For example, NIPT may be up to 98% accurate in predicting your baby’s sex. If the test detects a Y chromosome, your baby may be a boy. If the test does not detect a Y chromosome, your baby may be a girl.

How long does it take to get the results from genetic testing?

The amount of time it takes to receive your results from screenings or tests will depend on the test, the type of technology used, and the laboratory. In some cases, like with FISH, you may receive your results in just a couple of days. Other methods, like karyotyping, may take 1 to 2 weeks.

Is genetic testing covered by health insurance?

Some genetic testing may be included with your health insurance. Your coverage will depend on your policy and — in some cases — your risk factors, such as being over age 35, a history of genetic issues, or other reasons for testing as deemed necessary by your doctor. You can contact your health insurance provider for the specifics.

If you have questions or concerns about genetic testing, make an appointment with your doctor.

Testing is not required, but you can discuss the recommendations at a preconception appointment or at your first prenatal visit.

Most women will get negative results with both genetic screening and diagnostic tests.

For women who receive positive results, this information can be helpful with choosing further testing, receiving additional medical care, assessing pregnancy options or finding resources/support for after the baby is born.