Good genes: What parents-to-be should know about prenatal testing

Ready for the leap into parenthood? If you have a family history of genetic abnormalities, or simply want peace of mind for the health of your baby, prenatal testing may be a consideration.

All pregnant patients should be told about genetic testing options, according to the American Congress of Obstetrics and Gynecology.

Dr. Naomi Wahl (submitted photo)

Though Dr. Naomi Wahl, a perinatologist at Cape Perinatology Services, says most of her patients aren't concerned about genetic testing, she notes it can be an important step for some couples in learning whether their baby has a genetic issue and, if so, making plans for him or her to have the safest possible entry into the world.

"Some patients believe if their family history is negative for genetic issues, they do not have a risk of having a child with a genetic issue. Unfortunately, everyone has risks for genetic issues," Wahl says.

She says the most common topics she addresses include advanced maternal age, abnormal genetic screening tests and ultrasound findings that increase the risk for chromosome abnormalities.

"It might explain why a miscarriage or a stillbirth occurred and help assess risks for another pregnancy," she adds. "It can help determine where a baby should be born to give the baby the best chance to do well. It can prepare the family for a baby who may not survive through childhood or infancy. It can help prepare the patient and her family to be ready to care for the infant and be armed with information to allow the baby to reach its potential."

Dr. Jennifer Lovegreen (submitted photo)

Dr. Jennifer Lovegreen, an OB/GYN at Southeast Obstetrics and Gynecology, says genetic testing discussions occur in her office daily, with the most common topic being fetal chromosomal abnormalities.

"Aneuploidy is when there is an extra chromosome or a missing chromosome in a cell," she explains. "This typically occurs during cell division when the chromosomes do not separate properly. Down syndrome, or Trisomy 21, is the most common type of aneuploidy."

Lovegreen notes there is a difference between screening and diagnosing.

"Screening provides individual risk assessment and can only tell you if you are at low risk or high risk of having a baby with a particular abnormality," she says. "Diagnostic testing is more invasive and has more risks than blood tests, but can tell you if the baby has abnormal chromosomes."

Two common diagnostic tests are amniocentesis, or sampling the amniotic fluid, and chorionic villus sampling, or sampling the placenta, Lovegreen says. Because these two tests invade the fetal space, says Wahl, parents need to understand the risks of testing, such as potential pregnancy loss.

Noninvasive prenatal testing is a new advance in the field, says Lovegreen.

"It uses cell-free fetal DNA that comes primarily from the placenta and is found circulating in the pregnant mother's bloodstream," she says.

While it is not yet a part of standard lab work during pregnancy, Lovegreen says it is recommended in high-risk pregnancies, which include women 35 years or older, ultrasound findings indicating a high risk of aneuploidy, history of a previous pregnancy with trisomy, a positive screening test result or a parent carrying a chromosomal abnormality.

Lovegreen says about half of her patients choose to undergo prenatal screening tests.

"A common reason to obtain testing is to have peace of mind that there likely isn't a chromosomal abnormality, or if there is, to prepare for medical needs that may arise during the pregnancy or after delivery," she says. "If a patient has a positive screening test, we can get them in for the confirmatory diagnostic testing quickly to help answer the unknown."

Results that come back normal will be reassuring to parents, but abnormal results may require further counseling by the physician, genetic counselor or other specialist, Wahl says.

Melanie Baxter, a senior certified genetic counselor at InformedDNA, uses telemedicine to confer with doctors and patients all over the country.

"There are a lot of different fields of genetic counseling; cancer and prenatal are the biggest," says Baxter, who was trained in prenatal genetic counseling and has practiced in the cancer field for the past six years.

"It's a perfect opportunity for genetic counseling to reach into telemedicine," she says. "There are not enough genetic counselors in the country to keep up with the demand for genetic testing, especially for cancer."

Genetic counselors like Baxter work with patients and doctors to determine what testing is appropriate and coordinate the testing. Family history and insurance also are part of the discussion.

"The big questions that might come up are the basics of what genetic testing is, what it can tell you, and just as important, what it can't tell you," she says.

Baxter advises coming to a genetic counseling session with all your family medical history at the ready.

"You need to be prepared to answer a lot of questions about your family history. Sometimes patients don't realize how detailed we get about what's happened in their families," she says. "If you think that through before your appointment, it makes a huge difference. ... What's happened in your family guides counselors to what testing is going to be necessary. Try to make your history as accurate as possible. Preparation is a big thing."

Don't forget to jot down any questions you have about testing.

"There are no silly questions, because genetic testing is new for everyone," Baxter says. "Testing may not be appropriate for everyone, but if there is anything in your personal or family history that makes you wonder if genetic testing is right for you, then definitely ask a doctor about it or find a genetic counselor. We can use your family history to help in your medical management. That's why we push patients to realize that knowing their family history is really important."