Testing for Fetal Abnormality

Posted On: September 27, 2018 By CIW

Over the past several years, the ability to test for genetic fetal abnormalities has increased exponentially. In the past, women who were under the age of 35 were often told that they were low risk and that there was nothing they could do, while women 35 years and older were told that they needed to undergo invasive procedures to find out if their baby had a genetic abnormality. However, nowadays, with the advent of screening, this is no longer the case. Read on to learn more about the testing available for fetal abnormality at Carnegie Imaging.

What tests are available for fetal abnormality?

Noninvasive screens, which involve a series of blood tests and an ultrasound, can be done in women of all ages and provide a very precise estimate of the risk of having a baby with a genetic abnormality, specifically Down syndrome, trisomy 18, and trisomy 13.

Based on these numbers, a woman can make a better-informed decision on whether she wants to do an invasive test, or a diagnostic test, which is not a screening test.  It basically provides a yes or no answer. Those invasive options include the CVS which stands for chorionic villus sampling, and an amniocentesis.

Conceptually, a CVS and an amniocentesis are the same types of test. They are both invasive, involve a needle entering the mother, and provide the cells from the baby or the placenta. At Carnegie Imaging, those are tested directly to check the genetics of the baby. They are categorized as invasive since the needle goes into the mother’s body, and they are categorized as diagnostic because they provide a yes or no answer.

What are the differences between these tests?

The difference between these tests is mainly procedural. The CVS is done earlier in pregnancy, typically around 11 or 12 weeks, and an amniocentesis is done slightly later, typically around 16-18 weeks. During a CVS, a needle is guided into the placenta, and during the amniocentesis, a needle is guided into the uterus, into the fluid around the baby. In neither test does the needle actually go into the baby itself. Both of these tests provide diagnostic results.

In the past, many people used to think that CVS had a much higher risk than amniocentesis in regard to pregnancy loss, but much of the newer data shows that that’s not the case. The risk for both tests is well under 1% and seems to be about the same.

When choosing between these tests, women should consider a number of factors, including when they would like to do the test, why are they doing the test, and how far into pregnancy an issue was discovered. If something was picked up earlier in pregnancy, the appropriate test would be a CVS. If something was picked up later in pregnancy, an amniocentesis would be needed.

One of the advantages to doing a diagnostic, or invasive test like a CVS or amniocentesis over a screening test is you can test for more conditions. A screening test may look for a couple of genetic conditions, but an amniocentesis or CVS can check for over 100 conditions in the baby.

Why Choose Carnegie Imaging?

Here at Maternal Fetal Medicine Associates and Carnegie Imaging for Women, we perform both procedures and we believe that they’re both safe and reasonable procedures for women to choose, in the case that they find out on their noninvasive screening that they’re high risk, or if they just choose diagnostic testing over screening tests.

If you are interested in learning more about the services offered at Carnegie Imaging, contact our office today!

Carnegie Imaging for Women blogs are intended for educational purposes only and do not replace certified professional care. Medical conditions vary and change frequently. Please ask your doctor any questions you may have regarding your condition to receive a proper diagnosis or risk analysis. Thank you!

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