Prenatal Testing

Here’s an in-depth look at the screening and diagnostic tests you might undergo, and how some real couples dealt with the decisions and emotional issues involved.

ultrasound

WHO IT’S OFFERED TO: All women.

WHEN IT’S OFFERED: At about 20 weeks (also offered as part of the first-trimester screening).

WHAT IT SCREENS FOR: A wide variety of problems. “An anatomical survey of the entire fetus is typically conducted,” explains midwife Barbara McFarlin.

HOW IT WORKS: Using a transducer placed over the abdomen, sound waves create pictures of the fetus.

HOW EFFECTIVE IT IS: McFarlin says it detects approximately 50 percent of heart defects; O’Brien says it’s excellent at detecting NTDs. However, O’Brien adds: “Fifty percent of babies born with Down syndrome had normal ultrasound results.”

WHAT IF …? If ultrasound does detect a potential problem, you’ll need to decide if you want an amnio to determine whether it could be part of a chromosomal or genetic syndrome.

glucose screen
This test is done at weeks 26 to 28 to check for gestational diabetes (high blood sugar during pregnancy), which increases the risk of having a too-large baby and needing a C-section.

group B streptococcus
At 36 weeks or so, you’ll be tested for the presence of potentially dangerous bacteria that could be passed to the baby during delivery. It involves a painless swab of your rectum and vagina.

Issues to consider Perhaps the biggest issue surrounding prenatal testing is what you would do if a problem were detected. “Women think they have to terminate, but that’s not true,” McFarlin says. “You can continue the pregnancy and use that time to educate yourself about the baby’s condition, talk to other families dealing with the same issue, maybe even prepare for the delivery.” For instance, if the baby will need surgery for a heart malformation at birth, you can find a hospital with that capability and deliver there.

Testing involves many such big decisions—ones that your doctor may not be able to discuss at length. “A discussion about prenatal testing can take up to an hour, time that many doctors just don’t have,” O’Brien says, adding that knowing all the details of the various tests may not even be within their area of expertise. As a result, many doctors routinely refer patients to a genetic counselor, who specializes in this area. One important note: If a diagnostic test indicates a problem, get a second opinion from a perinatal (high-risk) specialist.