What You Need to Know About Prenatal Testing

Prenatal testing can provide valuable information about your baby, but expectant mothers often have lots of questions about the accuracy and risks of prenatal tests. It can feel overwhelming for many and create worry and concern over false positives or negative results. I’m committed to spending time to help my patients understand their options. It’s important to note that all prenatal tests are optional and expecting mothers have the right to decline tests at any time. As a Ft. Lauderdale high-risk pregnancy specialist, I want women to have the best resources for a healthy and safe pregnancy. Less invasive testing options are the new trend, but many of these options have limitations and still require additional testing and follow up.

The two types of prenatal tests are screening tests and diagnostic tests. Screening tests like cell-free fetal DNA is a blood test that help screen for genetic abnormalities whereas ultrasound screens for birth or structural defects.  Diagnostic tests on the other hand are usually conducted after a screening reveals a potential problem or performed if a mother is at high risk of having a baby with a genetic condition, such as cystic fibrosis. Diagnostics tests include Chorionic Villus Sampling or Amniocentesis.

Here is more information about each of the different types of tests:

Screening Tests

Carrier Testing

Carrier Testing is a blood test that can be done to determine whether you or your partner may be a carrier of any hereditary diseases such as Cystic Fibrosis, Fragile X, or Thalassemia. Carrier testing is something that I typically recommend during preconception counseling sessions so that you know what your risks are before getting pregnant. If you are of Jewish ancestry, it is also very important to undergo screening as there are common hereditary diseases that can be tested to identify if you or your partner carry the same genetic defect.  Carriers of these genes might be very healthy, and you would never know you are a carrier but many of these can be passed on to your child. Knowing your risk is of importance when planning for your baby.

Nuchal Translucency Screening

This screen is performed between the 11 and 14th week of pregnancy.  Nuchal screening is an optional part of a first-trimester screening that combines a maternal blood screening test or the cell-free fetal DNA screening test with an ultrasound to measure the fluid at the back of a developing baby’s neck. This is a common test that scans for abnormalities that may be an early sign of Down syndrome, Turner syndrome, or congenital heart problems.   percent of those babies with Down Syndrome.  Nuchal translucency should not be performed by itself, however, for a more accurate assessment of your risk, additional screening tests will increase the likelihood of detection. 

Non-invasive Prenatal Testing 

Non-invasive Prenatal Tests (NIPT) are newer blood tests that have become more popular in the last few years to detect chromosomal abnormalities such as Down Syndrome. These tests have created the trend of gender reveal parties as it also detects the gender as early as 10 weeks of pregnancy. NIPT is a simple test that requires blood drawn from a needle. The test evaluates fragments of the fetal DNA found circulating in your blood from your baby’s placenta.  This DNA can determine if there is an increased risk of giving birth to a child with a genetic disorder such as Down Syndrome, Turner Syndrome, and a few others but additional testing is usually required for confirmation if any abnormality is identified.

It is important to understand that while this test can tell whether your baby has an increased risk, it cannot actually diagnose your baby. It is a screening test, not a diagnostic test. That being said, most women who do undergo NIPT screening end up finding that their baby’s risk for a genetic condition is low.

Having a positive NIPT result does not always mean your baby definitely has a genetic condition, it is still important to monitor your pregnancy in the event that a positive result is received. This is when your OBGYN may refer you to a high-risk pregnancy specialist, otherwise known as a Maternal-Fetal Medicine (MFM) Specialist for counseling, guidance and support during your pregnancy

Diagnostic Tests

 Chorionic Villus Sampling  (CVS)

Chorionic Villus Sampling is a prenatal diagnostic test that takes a small sample of cells from the placenta to diagnose genetic diseases . CVS is preferred by many women because it can be conducted earlier than amniocentesis––between 10 to 14 weeks from your last menstrual period.   CVS can be performed transabdominally or transvaginally and is determined by the location of your placenta. Your perinatal specialist will determine the best approach . Risks to the procedure can include complications such as light bleeding, cramping, and in rare cases miscarriage.

CVS is a specialized diagnostic procedure and I’m one of the few providers in Broward County certified to perform CVS.  The best way to determine which diagnostic test is right for you is to schedule an appointment to learn more.

Amniocentesis

Amniocentesis is a procedure performed after the 16th week of pregnancy that allows a small sample of amniotic fluid that surrounds the fetus to be withdrawn for genetic assessment. Amniocentesis is one of the most accurate tests to detect chromosome abnormalities, neural tube defects and genetic disorders such as Down syndrome, cystic fibrosis and spina bifida. The risks of amniocentesis have lowered dramatically. Advances in ultrasound technology allows physicians to see the amniotic sac, which greatly reduces the risk of miscarriage or damage to the fetus.

The best way to know which type of testing is right for you is to talk with your OBGYN or with a high-risk pregnancy specialist, like myself. I am also available for genetic counseling, in which we can discuss the risks and benefits of various genetic tests that can be done throughout your pregnancy. I also provide consultation to those who have abnormal screening test results or those who are interested in diagnostic testing based on their history.

Schedule an appointment with me at Signature Perinatal Center and I can help you make an informed decision about what’s best for you and your baby.

If you found this article helpful be sure to check back here for future blogs and follow me on Facebook and Instagram for even more helpful pregnancy tips and information!.

 

Author
Sasha Davidson, MD

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