How Reliable Are Pre-Natal Genetic Tests? Doubts Saved One Child’s Life

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Some of the most popular DNA tests available right now are about figuring out the health of a future child.

Pregnant women are given a lot of options for pre-natal testing. Since 2011, a new kind of blood test —manufactured by five main companies — has been available to determine the sex and screen for possible genetic conditions in an unborn baby early on. At 10 weeks pregnant, a woman gives a blood sample.

When Stacie Chapman got pregnant at 41, she and her husband Lincoln were happy to take that blood test. They’d been pregnant before but had miscarriages. This time, they were hoping for a healthy pregnancy. And they really wanted to prepare.

“I was rooting for girl, he was rooting for boy,” Stacie said.

But when the results came back two weeks later, Stacie got a call from her doctor. She knew immediately it was bad news. The test — a brand called Maternit21 — had come back positive for Trisomy 18, also known as “Edward’s Syndrome.”

“She explained to me what that was, and how horrific it is, and how it’s not compatible with life,” Stacie said. “And that most likely would be a stillborn if the baby did survive to full term. It would survive maybe hours, maybe days, she said. It was a very small percentage of children with this who live to their first birthday.”

Stacie called Lincoln, who was on a business trip and was standing in an airport. He started sobbing.

“The call came, and my heart just dropped, you know? It was just one of the toughest calls to take in my lifetime,” he said.

The Chapmans were devastated. They say they did not want their baby to suffer. So they made an appointment to terminate the pregnancy the very next day. But later that night, the doctor called back and suggested they should wait. She said the test was relatively new and it could have been wrong.

They waited a long wait, eight weeks — Stacie convinced the whole time that she was carrying a child who would never survive. At 20 weeks pregnant, she had an amniocentesis, or an amniotic fluid test. And that’s where their story takes another expected turn.

The amniotic test showed their baby was totally healthy. No Edward’s Syndrome.

The pre-natal DNA tests are marketed for their accuracy and manufacturers say they are more accurate than previously available tests. The maker of the test Stacie took says that for high risk women a positive result for Edward’s Syndrome is right 97.6 percent of the time.

But several recent medical studies and an investigation by the New England Center for Investigative Reportingwhich appeared in the Boston Globe, cast doubt on the reliability of pre-natal DNA blood tests when they have a positive result for a disease.

A study published in the New England Journal of Medicine last year found that a positive result on one popular test — not the one Stacie used — could be wrong more than half the time.

Leading Ob-Gyn Dr. Michael Greene says tests like the one Stacie took are looking for the risk of disease, not actually diagnosing that a child will be born with it.

“As good as they are — they’re very good — but they’re still screening tests. They are not diagnostic tests. And it’s very important that both providers and patients understand that before any irrevocable action is taken on the basis of these tests,” Green says.

The maker of the test Stacie took says “the test is not a replacement for a diagnostic test such as CVS or amniocentesis” later in pregnancy and like some other manufacturers, recommends women have genetic counseling and the results be confirmed.

The Chapman’s son Sam is now a healthy, vibrant, rambunctious 18 month old.

Lincoln Chapman says he doesn’t think about what they almost did as much as he did in the beginning. But it still haunts them.

“From time to time. When he’s playing, or he does something funny, we’ll say, can you believe that he’s here and he almost wasn’t, you know?” he said.

“That’s why we’re telling our story,” Stacie says. “It’s not easy to tell the world ‘we made an appointment to have an abortion.’ Nobody wants to tell the world that. But if we can just have one woman who got that positive result not make a decision until she has (an) amnio, that’s why we’re doing this.” 

This story originally appeared on NBC News on May 22, 2015.

View Part 1 and Part 2  of NBC Nightly News’ Genetic Testing Series.

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How Reliable Are Pre-Natal Genetic Tests? Doubts Saved One Child's Life

Updated