If you’re pregnant or trying to become pregnant, then you no doubt have been to the doctor a few times to make sure everything is progressing healthfully. There’s a lot that can potentially go wrong in the development of something as complicated as a human baby, and your OB-GYN can help you sort through the various problems that could arise.
One way the OB-GYN does this is through the use of genetic screening tests. These tests take a number of forms, from simple blood tests (that analyze DNA) and ultrasounds (that look for structural abnormalities that could indicate a problem) to more invasive procedures. When you’re trying to become pregnant or soon after becoming pregnant, it’s important to talk with your OB-GYN about the range of tests that are available and which ones are most important for your situation. Consider asking these five questions when speaking with your doctor.
[See: The Fertility Preservation Diet: How to Eat if You Want to Get Pregnant.]
1. Which tests should I have? (And when should I have them?)
There are several kinds of genetic screening tests available to pregnant women, and some should be conducted prior to becoming pregnant, says Dr. Jennifer Smith, an OB-GYN with Consultants in Women’s Healthcare, Inc. in St. Louis. “Ideally, a woman should talk to her OB-GYN about genetic carrier screening before she becomes pregnant.” This type of screening determines whether you carry a recessive gene that could result in congenital abnormalities or diseases like cystic fibrosis, Tay-Sachs disease, sickle cell anemia and other conditions that can result when both parents have that recessive gene.
“Many people are carriers, but they only have an affected child when they reproduce with someone with the same carrier status,” Smith says. Therefore, it’s helpful to know your own carrier status for these various conditions prior to pregnancy, and if you’re positive, your partner’s status. When both parents are carriers of the same disorder, the chances that their offspring will have the condition are one in four.
Once you become pregnant, genetic screening shifts to determining how the baby is developing, and there are some non-invasive tests that can help your doctor determine whether your baby is developing normally. Prenatal genetic screening tests are conducted as blood tests and ultrasounds during the first trimester (three months) of pregnancy. The blood test, called a cell-free DNA test, extracts and analyzes fetal DNA from the mother’s blood. The ultrasound looks for structural abnormalities that may indicate a genetic or chromosomal problem. These tests can offer your doctor a window into the genetic profile of your baby.
These tests are “pretty darn good,” says Dr. Mary Jane Minkin, clinical professor of obstetrics, gynecology and reproductive sciences at Yale University School of Medicine, but they’re not 100 percent accurate. “They’re about 98 or 99 percent accurate on detection of things like Down syndrome. But none of the tests are 100 percent.”
Your OB-GYN will also conduct an ultrasound at a few points during your pregnancy. A first trimester ultrasound may look at nuchal translucencies — fluids at the nape of the neck that can indicate cardiovascular abnormalities and potentially some chromosomal abnormalities that have been associated with cardiovascular abnormalities. Ultrasounds can also help determine the baby’s sex.
Any ultrasound is more than just a photo op, Smith says. “When we do our ultrasound at 20 weeks, we’re not just looking for a cute profile picture. We’re really looking for a lot of other things, too,” such as structural abnormalities in the heart, brain, spinal column and limbs that might indicate a serious health problem that would change the birth plan. For example, she says, “I can deliver a baby with Down syndrome at a community hospital, because they generally do fairly well at delivery as long as they don’t have a cardiac anomaly.” But for other complications, your doctor may need the support of specialists that can only be found at a larger institution. “As an OB-GYN, I need to know what’s on that anomaly screen. I need to know what’s on that mid-trimester ultrasound. If the baby has a cardiac anomaly, then this baby needs to be born in a center with pediatric cardiology available. I need to make sure you have a safe delivery.”
2. What are these tests looking for?
Genetic screening tests are looking for evidence of genetic disorders, structural deformities or other indications that the baby’s health might be compromised. “The point of the test is to assess whether the patient has an increased risk of a fetal aneuploidy,” says Dr. Deanna Mascho-Cawley, an OB-GYN at Geisinger in Danville, Pennsylvania. “A fetal aneuploidy is when there’s one or more missing or extra chromosomes present.” Some of the conditions this test screens for are Down syndrome (the most common chromosomal disorder), trisomy 18, and trisomy 13, which are conditions that result from an extra copy of a certain chromosome. They are often associated with physical abnormalities and intellectual deficiencies and some babies born with these conditions don’t survive long. The test also looks for extra or missing sex chromosomes that can result in Klinefelter’s Syndrome, in which male children have an extra X chromosome, or Turner Syndrome, in which female children have a partially or completely missing X chromosome.
[See: The Best and Worst Exercises for Pregnant Women.]
3. What happens if there’s a positive result?
If one of your screening tests returns a positive result, the first thing to keep in mind, Minkin says, is “don’t flip out. There’s a really good chance this is going to be nothing.” Screening tests by their very nature sometimes return false positives or false negatives. No screening test is 100 percent accurate, so it’s important to stay calm and follow up with more testing to find out what’s going on.
Mascho-Cawley says you’ll be offered a second round of more invasive but also more accurate testing “to help determine with as much certainty as possible if a genetic condition actually exists. Diagnostic testing includes amniocentesis, which is where we insert a needle through the abdomen into the uterine cavity to get a sample of the amniotic fluid, or depending on the gestational age, chorionic villus sampling,” in which a small sample of cells from the placenta is analyzed.
Minkin says “the grandma of genetic tests was amniocentesis. It’s been around for about 40 years. And it’s close to 100 percent that you can tell exactly what’s going on genetically with the fetus.” But that accuracy comes at a cost, she says. “The drawback of amniocentesis is that it’s done at 16 weeks, when you’re already into the mid-trimester. If you’re thinking about a termination, that gets a little dicier.” Chorionic villus sampling,on the other hand, can be done a few weeks earlier, typically between weeks 10 and 13. “That’s done as a procedure through the cervix, although some people do have it done trans-abdominally, at the end of the first trimester. And it’s quite accurate as far as telling you what’s going on with regard to genetic abnormalities and the numbers of chromosomes.”
4. What are the risks and benefits of doing (or not doing) these tests?
Mascho-Cawley says the first trimester screening tests carry no risks themselves because they are “blood tests alone or blood tests and ultrasounds, so there’s no risk to mom or baby with the screening tests.” However, “you run the risks that the results can return abnormal,” which could lead to emotional distress for some patients.
Secondary diagnostic tests do carry slight risks to the fetus. “The diagnostic tests are more invasive and carry additional risks, although the risks of those procedures are rare,” she says. The Mayo Clinic reports that a second-trimester amniocentesis test carries a 0.6 percent risk of miscarriage. The procedure also carries a very slight risk of leaking amniotic fluid, needle injury or infection, transmission of infection to the fetus if the mother has hepatitis C or HIV/AIDS or transfer of fetal blood cells to the mother’s bloodstream that in rare cases can result in damage to the baby’s red blood cells. CVS testing carries similar risks, with the Mayo Clinic citing a 0.7 percent chance of miscarriage associated with this test.
Because of these slightly elevated risks, diagnostic tests like amniocentesis and CVS are rarely offered as the first option, but Mascho-Cawley says they remain a choice for any pregnant woman who wants that information. “According to the American College of Obstetricians and Gynecologists, any patient can be offered or should be offered that diagnostic testing as well. We just tailor the counseling based off the patient’s risk factors and their desires because of those additional risks that are associated with those procedures.”
5. What else should I consider?
Your OB-GYN should also counsel you to answer a few questions yourself during this process — namely what information do you want and how will you respond when you receive it? This may involve some “soul searching,” Smith says, a process which Minkin says is often best handled before you’re even pregnant. “Once you get pregnant, those tests in the first trimester happen quickly, so I think that’s something people should consider when they’re thinking about having a kid — ‘what would I do if I get a positive result?'” It’s a lot to consider during that short two months that most women have between discovering they’re pregnant and the end of the first trimester. “That’s not a long time for people to make such significant decisions,” Minkin says, so she encourages any woman considering becoming a mother to pursue preconception counseling to discuss the issues that genetic testing can raise.
[See: How to Cope With Gestational Diabetes.]
Smith says that if you’re certain that the outcome of genetic testing “won’t change the outcome of the pregnancy,” then the question becomes “is this information you want in advance? Do you want to be prepared, even if it’s not going to change the outcome of the pregnancy?” She says for some people, knowing in advance whether their baby will have Down syndrome, for example, can help them line up resources and make arrangements for the baby’s special needs. But others may find this advance warning upsetting and have a more stressful pregnancy. The only person who can answer the question about how having this information will affect you is you.
Lastly, Minkin also strongly encourages all women who are pregnant or trying to become pregnant to take folic acid, a vitamin supplement. “We usually say at least 400 micrograms a day” is the optimal amount, she says. This nutrient has been found to reduce the chances that your baby will develop spina bifida, a congenital spine deformity that can severely impact the child’s life and mobility. “It’s better to initiate after conception than not take it at all, but it’s ideal to have it on board when you conceive because we know it does diminish the chance of having a kid with spina bifida and all neural tube defects, and that it helps with other congenital deformities,” she says.
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What Should I Ask My OB-GYN About Genetic Screening? originally appeared on usnews.com
