When Tanya Lehrman got pregnant at 39, she didn’t want to take any chances. Though she hadn’t even had her first ultrasound yet, because she was older and had miscarried before, she was worried about her risk of having a baby with chromosomal abnormalities, like Down syndrome. But she was also concerned about testing for these issues: Her doctors told her that an amniocentesis—the standard test for chromosomal abnormalities—comes with a small chance of miscarriage. “We had worked so hard to get to that point that we just wanted to do everything that we could for the safety of the baby,” says the Montreal-based mother.
One doctor suggested she might want to try non-invasive prenatal testing (NIPT) instead. NIPT is a simple blood test that analyzes the baby’s DNA in the mother’s blood, looking for chromosomal abnormalities. It poses no risk to the baby, is 99 percent accurate and can be done as early as 10 weeks. It’s covered for high-risk moms in British Columbia, Manitoba, Nova Scotia, Ontario and PEI, and is available privately for everyone at a cost of $500 and up.
Lehrman, who lives in Quebec, paid $900 when she decided to go ahead with NIPT. About a week later, her doctor told her the test was showing a less than one percent chance for any chromosomal issues. “I had miscarried at about six weeks the last time, so I just wanted to do everything to prevent that from happening again,” she explains. “[The] gave me peace of mind.”
NIPT became available in 2013, and since then, it’s become increasingly popular among pregnant women as a lower-risk alternative to amniocentesis. But it can also be expensive, and it’s not a definitive tool for diagnosis. If you’re considering it, here’s what you need to know.
Your risk is key Everyone is given the option of being screened for genetic issues during routine prenatal care. Between 11 and 14 weeks, most women will have blood tests that look for certain proteins in their blood and an ultrasound, which includes looking for markers that could point to Down syndrome or trisomy 18 (a genetic condition that’s often life-threatening). Doctors use those indicators, along with your age, to calculate your odds of having a baby with one of these conditions. If your risk is higher than a given cutoff, say 1 in 350 (the cutoff varies by region), you’ll be classified as high risk. Women over 40 are also automatically seen as high risk. Of course, it’s up to you whether you want to know if you’re high or low risk—many women choose to skip screening for personal or religious reasons and choose to just be monitored to make sure the baby is healthy and growing well instead.
NIPT or amniocentesis for high-risk pregnancies If you’re high risk, your doctor or midwife will talk to you about the possibility of further tests. Enter NIPT: The test can detect up to 99 percent of babies with Down syndrome, as well as trisomy 18 and trisomy 13, both of which can cause severe physical and intellectual issues. It can be done as early as the 10th week of pregnancy—even before the first blood tests and ultrasound, which can be useful for women who are over 40 and know they are at a higher risk. The test is totally safe for the baby.
NIPT has a low false positive rate of approximately 1 in 1,000—when the test says there is an increased risk of a problem but there really isn’t one. But it’s high enough that, if you’re thinking of an abortion because of NIPT results, you’ll want to get an amniocentesis or chorionic villus sampling (CVS) test to confirm the diagnosis first. (You can also skip the NIPT and go straight to an amniocentesis or CVS test.) An amniocentesis, which can be done around 16 to 20 weeks, and a CVS, which can be done around 11 to 13 weeks, are diagnostic tests, which means they’re as close to 100 percent accurate as possible, but they also carry a miscarriage risk of about 0.5 percent.
Screening for low-risk women If early blood tests and your ultrasound don’t show any signs of heightened risk—as is the case for most women—you can carry on with routine care. Standard screening includes another round of blood tests at 20 weeks, and another ultrasound around then as well, to look for things like congenital heart defects, cleft lips and spina bifida.
Or you might choose to pay for NIPT anyway. And if you do get a positive result? Some women who have a positive NIPT will go on to get an amniocentesis or chorionic villus sampling while others will just use that as information to help them better prepare for their baby and for the birth. “It’s not just about whether they want to continue with a pregnancy or not,” says Nanette Okun, an OB/GYN and one of the authors of new guidelines around prenatal screening in Canada from the Society of Obstetricians and Gynaecologists of Canada and the Canadian College of Medical Geneticists.
Both NIPT and standard screening can “find issues that would change who should care for women,” says Okun, explaining that it might indicate a woman needs to move her birth plan to a hospital or switch from a midwife to an OB/GYN. Genetic counselling, which is offered before an amnio or CVS, can help you figure out what you want to do.
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