The first trimester can be a time of anxiety. In addition to the nausea, fear of miscarrying, and changes to your body and lifestyle, you have to navigate your genetic testing options. It's a personal decision, and some expecting parents may chose to forgo them altogether. But if you do decide you want to know your baby's risk, today there are various diagnostic and screening tests available, each with potential upsides and downsides.
In the past five years, a new test has become available. It's called Non-Invasive Prenatal Testing (NIPT) or cell-free DNA testing (cfDNA). Because it's new, it has yet to make it into the mainstream list of testing options presented to many women. But after doing my research, I decided it was the right option for me. Here's why.
How the NIPT Works
The NIPT is a simple blood draw that can be done as early at 10 weeks. I chose the test offered by Harmony. Other companies who offer it include Genesis Serenity, Natera, and MaterniT21. The test I took screened for Down Syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), and Patau syndrome (Trisomy 13), the most common chromosomal problems.
The NIPT is a simple blood draw that can be done as early at 10 weeks.
Here's an overview of how it works: while you're pregnant, some of your fetus's DNA enters into your blood. At 10 weeks, there is enough fetal DNA to analyze. Once blood is drawn and sent to a lab, they look for an imbalance of chromosome that may signal a problem. For example, if there are too many chromosomes 21 in the blood, that suggests a high risk of Down Syndrome, which is caused by the presence of three copies chromosome 21 instead of the typical two copies. The test can also determine the sex of your baby. If it picks up any Y chromosomes, it must be a boy since we know mums have none. If no Y chromosome is found, the test can tell you with high certainty that you're having a girl. All of the final results take five to seven days.
I first found out about the NIPT by reading Emily Oster's book Expecting Better. Using her background as an academic researcher in economics, Oster analyses studies on everything from coffee to deli meat into easy to understand suggestions for pregnant women backed up by data. I found the section on genetic testing to be a great introduction to all my options.
Oster compares the new NIPT screening test with the more traditional "integrated screening test," which combines a first trimester nuchal translucency ultrasound and blood test with a second trimester blood test to assess risk. She also discusses the amniocentesis and chorionic villus sampling (CVS) diagnostic tests. Unlike screening tests, the amniocentesis and CVS don't simply assess risk but tell you for certain if your baby has chromosomal problems. But they also come with a risk of miscarriage. Knowing this, I decided my first step would be a noninvasive screening test. In her book, Oster concludes that the NIPT screening test was superior to the traditional integrated screening test. I decided to weigh the pros and cons, too.
The Benefits of NIPT
- You can do it earlier. The NIPT can be done at 10 weeks, while you have to wait until week 15 or 16 to complete the final stage of the integrated screening. I considered genetic testing an important milestone in my pregnancy and was happy to have a chance to do it earlier.
- It's a simple blood test. Unlike the integrated screening, which includes an ultrasound and two blood tests, the NIPT is just one straightforward blood test. This means that unlike the integrated screening, your results won't be somewhat dependent on the training of the ultrasound technician.
- It's highly accurate for the most common chromosomal disorders. These include Down Syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), and Patau syndrome (Trisomy 13). For example, the NIPT will detect at least 99 percent of Down Syndrome cases, compared to the sequential screening that will detect 90 out of 100 cases of Down sydnrome.
- It's safe for the baby. Invasive screenings like the amniocentesis and CVS will tell you with certainty if your baby has a chromosomal issue, but they come with a risk of miscarriage. Like the integrated screening test, the NIPT does not carry this risk.
- You can find out the sex sooner. With a simple blood test, you can find out the sex of your baby at 10 weeks, instead of waiting for an ultrasound at around 16 to 20 weeks.
- Studies suggest the NIPT has a lower false positive rate. Oster cites stats that show that for every 100 women who take the older test, six will be told there may be a chromosomal problem when there isn't one. For the new test, only 5 women in 10,000 will be falsely told they have an issue. There is still a possibility you will have to worry unnecessarily, but it's less likely. If you do get a positive, your next step would be an amniocentesis to confirm.
The Downsides of NIPT
- It looks for a limited number of problems. The NIPT is really good at detecting the most common chromosomal problems, but not some more atypical ones. When explaining my options to me, my doctor made sure to emphasise that the traditional integrated screening tests also looks for early preeclampsia and other structural issues issues, including anencephaly, open spina bifida, abdominal wall defects, and Smith–Lemli–Opitz syndrome (SLOS). If you opt for NIPT, you'll want to ask your doctor about additional screening options for structural issues and preeclampsia.
- It may be more costly. Many insurance companies will only cover the NIPT for women over 35, so be sure to talk to your provider about it. Out of pocket it cost me $408 (USD).
- You may need help interpreting the results. I had a great experience with my genetic counsellor, who explained each possible result ahead of time and answered my questions with patience. Since there is still a risk of a false positive, you want to make sure you have professional help and support for interpreting the results.
- It doesn't work for everyone. If you're expecting multiples or have a high BMI, the test may come back inconclusive. Research suggests that about 5 percent of women get no result at all.
- It's new. In 2015, the American Congress of Obstetricians and Gynecologists (ACOG) said NIPT needs to be further evaluated before it will recommend the screening for all pregnant women. If you're the type of person who likes to go with the "tried and true" medical procedures, even if the new one might prove superior over time, NIPT might not be for you.
One study comparing the NIPT to the traditional integrated screening determined that the main downsides of NIPT include the cost, inability to detect structural issues and uncommon chromosomal problems, and the five percent failure rate. Still, the study's author concluded: "Patients should be told about the availability of NIPT as an alternative but expensive screening method with a better detection rate and a lower false positive rate." For me, these last two points made it worth it.