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? Continue reading