Prenatal Expanded Carrier Screening Tests Can Be Difficult To Interpret : Shots - Health News A variety of genetic tests are available to screen both fetus and parents. One option that's growing in popularity is called an expanded carrier screening. The results can be useful and overwhelming.

Prenatal Testing Can Ease Minds Or Heighten Anxieties

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So one of the fastest growing markets for genetic testing is for future parents who want to know their risk of passing something onto their child. But more genetic information does not always make decisions easier and can result in more worry. Lesley McClurg from member station KQED explains.

LESLEY MCCLURG, BYLINE: Myriad Genetics is one of about a dozen labs vying for the business of concerned future parents.


UNIDENTIFIED PERSON: The foresight carrier screen can detect over 100 health conditions that can be passed unknowingly from parent to child.

MCCLURG: Finding out whether parents could pass along a few serious diseases isn't new - that's been happening for the last few decades. What's new is screening parents for hundreds of very rare conditions. It's called expanded carrier screening. If you take Myriad's test, your sample is sent to a lab in South San Francisco, where Gifty Hammond showed me around.

GIFTY HAMMOND: This is a robot that takes the blood and saliva and separates out its DNA.

MCCLURG: Then robots will sequence the genetic code, scanning for irregularities. Even healthy parents can sometimes pass a disease onto their child if they both carry a mutated version of the same gene. Shara Watkins worried this could be the case for her. She was three months pregnant, and there's a history of disease in her family. Her mom has lupus, and her half-brother has cystic fibrosis. Plus...

SHARA WATKINS: I had a high-risk pregnancy, and there had been a lot of complications prior to this, and so I wanted to know everything because I was anxious about everything.

MCCLURG: Shara's doctor prescribed an expanded carrier screening from another Bay Area company called Natera. Shara learned she was a carrier for spinal muscular atrophy. So her husband Robert also took the test, and then they got a startling email from their doctor.

S WATKINS: Robert has also tested positive for this. I'm not exactly sure what it means. You should see a genetic counselor immediately.

MCCLURG: The couple hadn't discussed what they would do if their baby was at risk for spinal muscular atrophy.

S WATKINS: So I called Rob in pure hysterics.

ROBERT WATKINS: When I got the call in my office, she was crying. We were both kind of in a panic mode immediately.

MCCLURG: So they booked an appointment in the genetics counseling office at Stanford University.

MEG HOMEYER: So this is the actual report.

MCCLURG: Meg Homeyer was part of the counseling team. Seeking outside expertise is a crucial step for many parents to put test results in context because, as it turns out, Shara, Rob and their doctor thought their risk was a lot higher than it was.

HOMEYER: They came to us with this information, not knowing what it meant, what the risks were and not understanding the implications.

MCCLURG: So they thought it was 1 in 4. What was it actually?

HOMEYER: It was much lower. I think it was 1 in 3,500.

MCCLURG: But even though Rob and Shara's worst fears were wrong, they still lost sleep at night wondering if their child could be the 1 in 3,500. To know for sure, they would have had to do more diagnostic testing, which could put the pregnancy at risk. Homeyer says she sees many parents agonize over emotional decisions based on abstract numbers.

HOMEYER: They will not have that answer, potentially until that baby's here, and in the meantime, they're in this gray area where they're trying not to worry, but they can't help it.

MCCLURG: And so is it valuable, do you think, for folks to have this information?

HOMEYER: It depends on the family, and I think that's the hard part, is that there's the family that will want every possible test available. They'll want no stone unturned because their tolerance for risk is low. There are other families where this information in pregnancy isn't useful for them.

MCCLURG: Like families who wouldn't terminate a pregnancy, regardless of the results. And Homeyer stresses that parents remember.

HOMEYER: The sheer numbers are that 96, 97 percent of the time, a baby is born healthy.

MCCLURG: That was the case for Shara's little girl, a healthy five-month-old.

So looking back, if you could, like, rewind all the way back, would you do a career screening again?

S WATKINS: I think so. I think so, yeah.

MCCLURG: In the end, she says the anxiety she dealt with was better than not knowing anything at all. Her advice to future parents is to really think about whether more information will, for them, be reassuring or just another thing to worry about. For NPR News, I'm Lesley McClurg.


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