What Is Genetic Screening For Pregnancy? A Certified Nurse Midwife Explains

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As you round the corner into your second trimester (hopefully kissing the worst of morning sickness goodbye), your doctor or midwife will likely begin talking about your option of undergoing a genetic screening test. If the conversation itself has you breaking out in sweat, you're not alone; pregnancy can be an emotionally vulnerable time and expectant mothers have a lot on their minds. But what is genetic screening for pregnancy? The test is meant to be a tool to serve and prepare you, not to fill you with anxiety, and it's a valuable tool to have.

Certified Nurse Midwife Patricia Evans of Fountain Valley, California tells Romper that first and foremost, women should understand that these tests are not required, and only you can decide if they are right for you and your family. When it comes to invasive prenatal tests in particular, it is important to weigh the benefits against the risks, which, it should be noted, includes a small possibility of miscarriage.

The difference between invasive and noninvasive tests is that while invasive ones involve needles or probes being inserted into the uterus, noninvasive tests are simple blood draws; because did you know that pieces of your baby's DNA are already floating in your blood stream?

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In the first trimester, you may choose to do a genetic screening consisting of a blood draw and a specialized ultrasound called Nuchal Translucency. The blood draw is done between weeks 10 to 14 and the ultrasound, which measures the thickness of the fold on the baby's neck, is done between 11 to 14 weeks. According to Evans, after both tests are completed, you will be given a preliminary result for Trisomy 18 and Down Syndrome.

In the second trimester you may do a second genetic screening consisting of only a blood draw. This is performed between weeks 15 to 20 of pregnancy and can be done with or without the first trimester screening. The birth defects included in this screening are Down Syndrome (Trisomy 21), Trisomy 18 and 13, Smith-Lemli-Oitz Syndrome (SLOS), and Neural Tube and Abdominal Wall defects.

Although these tests help parents identify and prepare for complications earlier, Evans says that many problems can be caught by a standard 20-week ultrasound. "This is a comprehensive ultrasound and checks the brain, face, lips, heart, organs, extremities, placenta, cord insertion site into the placenta, number of vessels in the umbilical cord, and the amount of amniotic fluid," she tells Romper. While many parents are more excited about finding out the sex at this ultrasound, there's a reason it's called an "anatomy scan" and not a gender reveal party.

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Invasive tests have declined in popularity thanks to the accuracy and low risks of the non-invasives. Chorionic Villus Sampling (CVS) and Amniocentesis are the two types of invasive genetic testing. CVS requires a small piece of the placenta to be removed from the uterus with a needle, and Amniocentesis draws a small amount of amniotic fluid from the uterus by a needle through the abdomen. Both tests look for genetic abnormalities in the growing baby.

Evans encourages parents to ask themselves discerning questions when making the decision to undergo genetic testing. These include, "Do we have a family history of birth defects and if so, what is this baby's risk?," "What will we do with the results of this test?," and "If insurance does not cover testing am I willing to pay out of pocket?".

For some moms and dads, knowing the likelihood of facing birth defects is an important part of their preparation process. For others it is a source of anxiety they would rather do without.

Check out Romper's new video series, Bearing The Motherload, where disagreeing parents from different sides of an issue sit down with a mediator and talk about how to support (and not judge) each other’s parenting perspectives. New episodes air Mondays on Facebook.