Expecting, But Not This: Prenatal Blood Tests Can Reveal Moms' Health Problems

(Flickr Creative Commons)
(Flickr Creative Commons)

Since 2011, well over a million pregnant women have chosen to use new, non-invasive prenatal tests that let them check the chromosomes of the fetus they carry with just a blood draw, avoiding the risks of an invasive procedure like an amniocentesis.

But recently, it has become clear that these new, non-invasive tests, which aim to test fragments of fetal DNA floating in the mother's blood, can produce a surprising side effect: unlooked-for findings that the mothers — not the babies — have chromosome anomalies, or even cancer.

According to a commentary just out in the journal Nature, as of late last year, "at least 26 pregnant women with abnormal blood-test results later learned that they had cancer." To cite a recent Buzzfeed headline: "Pregnant women are finding out they have cancer from a genetic test of their babies." Dr. Diana Bianchi, executive director of the Mother Infant Research Institute at Tufts Medical Center, writes in Nature:

Parents, obstetricians and physicians have been taken by surprise. Consent forms used by test providers rarely mention the possibility of findings concerning the mother’s health. And caregivers have little guidance on what to do when such findings arise. Test providers need to rethink their consent forms to prevent unwarranted confusion and anxiety — not least, women deciding to terminate their pregnancies on the basis of wrong interpretations of test results.

Dr. Bianchi's comments are aimed mainly at the medical world, but I asked her what her message was to the many pregnant women out there who may get DNA findings that raise concerns. Her bottom line: "Slow down. Pregnancy is a very emotional time. Get the information you need, take a deep breath."

(For help slowing down, pregnant women might read this incisive report by Beth Daley of the New England Center for Investigative Reporting on how the accuracy of prenatal DNA tests is oversold and often misunderstood.)

Pregnant women need to know that when their blood is being drawn for testing on their baby, their own DNA is being tested as well.

Beyond caution on the test findings, Dr. Bianchi said, "I think that pregnant women need to know that when their blood is being drawn for testing on their baby, that their own DNA is being tested as well, and oftentimes that is not mentioned as part of the pre-test counseling, if any pre-test counseling is occurring."

So, I asked, there is a small chance that there could be some incidental finding – either that they have cancer, or that they may have a sex chromosome abnormality?

Yes. The maternal incidental findings are quite rare, but some of them have medical significance, such as finding a tumor that the woman didn’t know that she had. In other situations, women who are pregnant are very surprised to find out that they themselves have a chromosome abnormality.

Would that matter very much?

Well, for example, DiGeorge syndrome is an area that is currently being actively discussed because it’s not something that’s been previously screened for in the past. So, finding out that you have a diagnosis of DiGeorge syndrome really does impact upon your health and would mean that you would need follow-up testing and certainly examination and discussion with geneticists and other medical providers.

And I can imagine that the emotional distress can also be incredible, right? Just when you most need to live and take care of another human being, you’re being told there’s something wrong with you.

I think it goes both ways. For me, a very important conclusion from this commentary is that a pregnant woman who finds out that she has an abnormal prenatal testing result really needs the follow-up diagnostic testing, and by that I mean the amniocentesis or the CVS [chorionic villus sampling] to confirm that the abnormality is in the fetus. Because, in the cases that we’re discussing here, the fetus has a normal chromosome test. So, it’s very important not to react immediately and take action immediately of any kind; it really is very important to slow down and get all of the available information.

You mentioned in the commentary that six percent of women who get an abnormal finding terminate the pregnancy before getting the actual diagnostic test.

Well, that was in one study that we know of, but it’s been a widely quoted study. It does raise the alarm that people are not taking the time to get all of the information.

And, meanwhile, these new kinds of blood tests are, from what I saw in a recent BuzzFeed article, incredibly popular. They were adopted surprisingly quickly.

Yes. It’s one of the largest- and fastest-adopted genetic tests in history — actually, any medical test in history, and one of the things that I found in writing this article was that a minimum of over 1,500,000 tests have been performed to date since it first became available in 2011. So it’s really, really changing the way prenatal screening and diagnosis are performed.

And there’s so much we still don’t know about genes and their effects, right? You can find anomalies that may mean something, or they may not. That's the state of the science?

Yes, I think there are two take-home messages. One is that every individual human being, even people who are supposedly normal, are very complex at the DNA level. And the second message is that none of the people practicing medicine today are getting enough genetic education. So, it’s a tremendous challenge because the technology is outpacing our ability to both provide care and to accurately counsel patients as to the implications of the findings.

It does sound like there are a lot of gaps in the system.

Well, one of the reasons why I wrote the commentary was that I thought it was very important to shine the light on the maternal half of the equation. There’s been a lot of discussion about incidental findings in genetic testing in general, but the unique situation in pregnancy is you’re testing two people at the same time.

There’s a potential upside as well, right? You could find out, for example, that a mother has cancer and cure her, and she goes on to raise the baby.

Well, that’s certainly the hope, but the test is not designed nor certified for cancer testing. The important thing, as I said, is, when you get the abnormal results, first of all, confirm whether or not they’re present in the fetus. If the fetus is normal, then this means that we need to look further for an explanation of these results.

Readers, thoughts? Reactions?

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Carey Goldberg Editor, CommonHealth
Carey Goldberg is the editor of WBUR's CommonHealth section.



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