Prenatal Test Prep

By Published On: November 1st, 2016
Home > Pregnancy > Prenatal Care > Prenatal Test Prep

Congratulations! The results are in, and you have a bun in the oven. But don’t think that’s the only test you have to pass—there are still plenty more to come.

If you’re expecting, prepare to be the center of some major medical attention. There will be lots of tests (more than you took in high school!), and you’ll clock serious face-time with your health care provider. But it doesn’t mean that there’s something wrong. In fact, an onslaught of prenatal screening tests and checkups is the norm for pregnant ladies. The pokes and prods are all to make sure you and your peanut are in tip-top shape.

Prenatal testing gives your practitioner insight into how mom and baby are faring throughout the pregnancy, and in the case of genetic testing, it can also indicate if baby might have any birth defects or chromosomal abnormalities.

Want to know what’s necessary and what’s not? Our study guide is here to clue you in to the most common prenatal tests, why they’re important and what you can learn from them.

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Routine Tests

Your first visit to your doctor or midwife will include a physical exam and a bunch of paperwork to go over your family history, current health conditions and risk factors. You’ll also have to take a urine and blood test. These standard tests will look for issues that could affect your pregnancy like infections, STDs, anemia and diabetes.

Get used to peeing in a cup because you’ll be doing it frequently. A urinalysis tells your practitioner if you’re fighting off an infection, have high glucose levels (an indicator of pregnancy-induced diabetes) or are at higher risk of preeclampsia, a serious issue during pregnancy that causes high blood pressure.

Besides multiple urinalysis tests, another blood sample will be taken later in pregnancy to double check that everything’s going well. There are also two more tests you’ll receive in the latter stages of pregnancy …

Glucose screening and glucose tolerance test, 24 to 28 weeks

You’ll arrive at your appointment and be given a drink packed with glucose. (In other words, it’ll be super sugary.) One hour later your blood will be drawn to check your glucose levels. If the initial screening shows a higher than normal result, you’ll be asked to come in again for a more in-depth test called the glucose tolerance test. This three-hour procedure requires you to fast and then have your blood drawn before—and multiple times after—downing another bottle of that saccharine drink. The results will indicate whether you have gestational diabetes, or high blood sugar during pregnancy.

Group B strep screening (GBS), 35 to 37 weeks

Your OB will swab your vaginal area to test for a type of bacteria that many pregnant women carry. The bacteria can be passed to your baby during vaginal delivery, and although it causes you no symptoms and doesn’t affect a majority of babies, it can cause some newborns to become sick. If you test positive for the bacteria, you’ll receive antibiotics at the start of labor.

Genetic Testing

Early on during your pregnancy, you’ll be given the option of undergoing screening tests to look for genetic disorders. The screenings search for certain abnormalities, and the results are an estimate of whether your baby is at increased risk for the associated medical conditions. Whether you move forward with genetic screening is entirely up to you.

Carrier screening, preconception to 12 weeks

Based on your background, you may be offered a genetic screening for a single disorder like cystic fibrosis, sickle cell disease or Tay-Sachs disease. These disorders are passed down from parents and are more common in certain ethnic groups. A blood draw from the parents is needed to evaluate the chance of a baby inheriting one of these diseases.

Cell-free DNA screening (cfDNA), 9 to 10 weeks

One of the newest screening methods for Down syndrome and two other chromosomal disorders, cfDNA analyzes the particles of your baby’s DNA found floating in your blood. It’s usually offered to high-risk patients for whom the results are most accurate.

First trimester screening, 11 to 14 weeks

This screening requires both a blood draw and a specialized ultrasound (to analyze folds in your baby’s neck) between weeks 11 and 14. Those two tests, combined with your age, are used to determine the likelihood that your child has a genetic disorder like Down syndrome.

Triple/quad screening, 16 to 18 weeks

This test also looks for genetic disorders. It’s performed on one blood sample drawn between weeks 16 and 18. The triple screen looks at two hormones and a protein found in your blood. The quad screen looks at those as well as an additional protein.

Integrated screening, 11 to 18 weeks

This best-of-both-worlds screening combines the first trimester screening and the quad screening to give you the highest possible detection of Down syndrome and other genetic disorders, along with the ability to identify possible neural tube defects like spina bifida. In total, it requires two blood draws—one in your first trimester and one in your early second trimester, along with a specialized ultrasound.

Keep in mind that even though a screening might come back positive for a genetic disorder, it does not mean that your baby actually has the condition. “Genetic screening tests are intentionally set with a very high false positive rate because they are trying to catch all the possibilities, and then weed through them with an additional test,” cautions Robin Blumer, MD, OB/GYN in Southfield, Michigan. “Screening tests never make a diagnosis. They simply identify enough reason to offer diagnostic testing.”

Diagnostic Tests

If you receive a positive result from one of the screenings, try not to stress. “It’s more convincing that there is a problem if you see evidence of a major abnormality on a good ultrasound or on the more definitive diagnostic tests than on a screening,” explains Blumer.

Think of a screening as the first step in evaluating your child’s likelihood of having a genetic condition. After a positive screening result, the next step is talking to a genetic counselor and determining if you’d like to have a diagnostic test performed.

Depending on your stage of pregnancy, you will be offered the following tests, both of which search for further evidence of genetic disorders and birth defects by evaluating cells from your baby found in surrounding matter:

Chorionic villus sampling (CVS), 10 to 13 weeks

A needle is inserted into the abdomen or cervix to remove a small piece of placenta tissue for analysis.

Amniocentesis, 15 to 20 weeks

A needle is inserted into the abdomen to withdraw a very small amount of amniotic fluid for analysis.

Diagnostic tests offer more concrete results but can also cause miscarriage in a small number of pregnancies. According to the American College of Obstetricians and Gynecologists (ACOG), the estimated risk is that one miscarriage will happen out of every 300 to 500 amniocentesis or CVS procedures performed.

Like genetic screenings, diagnostic tests are optional. Some parents choose not to have them performed. Others use the diagnostic test results to make health care decisions and prepare for the adjustments a baby born with health problems requires. Weigh the decision with input from your OB and genetic counselor and discuss it with your partner to determine what’s right for you and your family.

Non-Stress Test

Feeling your little one swim around inside you is a highlight of pregnancy. But if your baby suddenly seems less active, your practitioner might call for a non-stress test (NST). The NST is a common test, used in third trimester, to check a baby’s heart rate and make sure your little one has adequate oxygen. It’s used when a baby has reduced movement or if you’re past your due date, have had complications with previous pregnancies or have complications with your current pregnancy.

The test requires 20 to 40 minutes of lying down with two belts strapped across your belly. One will track uterine contractions, and the other will monitor your child’s heart rate to see if it changes when she moves.

If the results are non-reactive (meaning your baby’s heart rate did not increase with movement), it could simply signal that your child was asleep or inactive. If you’re full term, your OB might recommend delivery after a non-reactive result. If you’re not full term, additional tests will follow and may include another NST at a later date, an ultrasound and/or a stress test that forces a uterine contraction.

Pregnancy is a time of rapid changes, but there’s no need to fret. Your prenatal care team is there to monitor and make sure you and your baby get the best treatment possible, so the excitement of bringing a wee one into the world can remain your primary focus.

By Kristi Valentini

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