What prenatal testing can tell you

Cindy Babcock, of Peterborough, Ont.,  has known since the age of four she is a carrier for a rare metabolic disorder. Cindy’s mother gave birth to two baby boys after Cindy was born — both died within three days. Her mother, a nurse, refused to accept the diagnosis of SIDS and pushed for answers. Doctors finally determined that the boys had died from ornithine transcarbamylase deficiency (OTC). “In normal people, food intake changes into ammonia, and then from ammonia into urine,” explains Babcock. “But with OTC, it does not get past that ammonia stage, so the body basically gets poisoned.”

Babcock chose to be tested for OTC when she became pregnant with her daughter, Natasha, 10 years ago, even though she knew that she would carry the pregnancy to term, no matter what. After a specialized test that was part of her amniocentesis, she was thrilled to learn that Natasha did not have OTC — in fact, she wasn’t even a carrier. “It was the best news,” says Babcock. Several years later, however, Babcock became pregnant again. And this time the news was not so good. Born with OTC, her baby boy, Colin, lived for just three days. Babcock takes comfort in knowing that “he was loved the whole time” and he died surrounded by friends and family. “It may have been a short life, but it was still a life,” she says.

Her situation brings up one of the misconceptions regarding prenatal testing, says Doug Wilson, a reproductive geneticist and department head of obstetrics and gynaecology at the University of Calgary. All prenatal tests are optional and “people think that if you have no intention of terminating a pregnancy, there’s no reason to have prenatal testing,” he says. “But the tests have nothing to do with the choices you make afterward.”

Even if you’re planning to continue your pregnancy, says Wilson, it’s important to know whether your child has a chromosomal abnormality or another genetic condition “because it’s going to improve the care that your fetus gets.” You might choose to deliver in a hospital that has specialized facilities available, for example, and you get the opportunity to prepare yourself and your partner, family and friends in advance.

The field of genetic testing is getting more sophisticated all the time. Here’s a guide to what the various prenatal tests are supposed to determine and why you might want to know.

The testing process The first tests you’re likely to have are screening tests. They’re not 100 percent accurate. Instead, they’re intended to flag your risk of having a baby with certain birth defects, most commonly Down syndrome, trisomy 18 and open neural tube defects, such as spina bifida. Many of us will float through these early tests without any issue. “That doesn’t guarantee a healthy child,” points out Mireille Cloutier, a certified genetic counsellor in Ottawa and spokesperson for the Canadian Association of Genetic Counsellors, “but it’s certainly reassuring.”

If you do screen positive, advises Wilson, keep in mind that doesn’t mean you’re a true positive. “Age is one of the factors we take into account when assessing the results, so most women who are 40 or older will have a screening test and it will come back as positive.” Don’t panic, he advises. But you now face your first tough decision: namely, whether to go on to a diagnostic test like CVS or amniocentesis that can tell you with almost 100 percent certainty whether your child has some of the more common congenital conditions.

Regina, Sask., mom Rhonda Grant Shaw chose to stop before a diagnostic test. She underwent a routine screening test about 12 weeks into her pregnancy that flagged her child as being at higher risk for Down syndrome. After an “alarming” phone call, Grant Shaw spent a day at a local maternity hospital undergoing a detailed ultrasound and a series of tests that failed to confirm the diagnosis. At that point, she was offered an amniocentesis. “My (now ex-) husband and I went for a walk and we spent a couple of hours trying to decide if there was any benefit to having the test,” she says. “Was it worth the risk if it triggered a miscarriage? We decided that we didn’t want to take that chance, so we left the hospital that day not knowing.”

Grant Shaw’s son, William, now 14 years old, was born several months later with Down syndrome. She admits that, initially, she felt overwhelmed by the diagnosis, “but the doctor’s approach was absolutely right,” she says. “We asked him what this meant. He said, ‘I have two sons myself and I don’t know what the future holds for them. But our job as parents is the same: You have to do your best to give your child all the opportunities you can."

The ultimate choice Parents who undergo a diagnostic test face the ultimate decision if the test comes back positive. At that point, says Wilson, there are only two options: “to continue with the pregnancy or to terminate.” Genetic counsellors like Cloutier can sometimes help with the decision making. “It’s a difficult choice,” says Cloutier. “I’m satisfied when I think people have considered all the things they need to consider.” She suggests, among other things, you take into account your own view of disabilities, your values, your resources and finances, and the impact on your existing family.

Ultimately, she says, each couple must do what’s right for them, and no one else can make that decision for them. In fact, while it’s difficult to find anyone who will talk about having made the choice to terminate, the Canadian Down Syndrome Society says that approximately 90 percent of parents choose to end their pregnancy after Down syndrome is diagnosed. “People feel judged for their choice,” says Cloutier. “That’s why they kind of hide out. But no one knows what they would do until they’re actually faced with it.”

Grant Shaw says she would never condemn anyone for making the decision to terminate. “I believe in a woman’s right to choose,” she says. But do make sure you have all the facts, she cautions. “I think there are lots of misunderstandings about what a life with Down syndrome is like, for example, and I feel a lot of people make that decision without knowing what it can be.”

Those who do opt to continue their pregnancy can benefit from knowing they may need access to a specialized medical team or facilities, particularly if they live in a more remote area of the country. Babcock, for example, gave birth to her second child at Mount Sinai Hospital in Toronto, which deals with many high-risk births. After Colin was born, she was given a care-by-parent room where family and friends could visit at any time of the day or night. “Especially for my mother, it was really healing,” says Babcock. “Her babies got taken away as soon as they got sick. She didn’t even get to hold them.”

It took Babcock several years to get over the devastation of Colin’s death and a subsequent miscarriage, and try again. But in February 2011, she once again became pregnant. In May, she underwent testing to determine if the baby had OTC. Unfortunately, the results were positive. But knowing about the condition in advance has enabled Babcock and her husband to seek out a potential treatment option through Toronto’s Hospital for Sick Children. “We’re not sure if it will be viable for us, but it provides a bit of hope that we did not have last time,” she says.  “Knowledge is power.”

This article was originally published in December 2011. 

Read more: The gifts of a child with Down syndrome> The cost of raising a special needs child> Miscarriage and pregnancy loss>