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Don’t worry. The Risk of Amniocentesis Causing a Miscarriage Is So Small It Might Be Zero.

Many women shy away from amniocentesis for fear of miscarriage—but the link between amniocentesis risks and miscarriage has been widely overblown.

 

The risk of amniocentesis causing a miscarriage has been wildly overblown.

In a heart-wrenching Moth video that went viral, Comedian Bethany Van Delft describes how fear of a miscarriage risk prevented her from having an amnio when she became pregnant in her 40s:

 

“The tests, the tests came with a risk of miscarriage, and I had already had two miscarriages.”

 

Her baby was born with Down Syndrome. The diagnosis came as a shock, because “the prescreenings showed no signs of Down Syndrome. None of the ultrasounds showed any sign of Down Syndrome.”

We do not know how many pregnant women like Van Delft shy away from amniocentesis (amnio) and chorionic villus sampling (CVS)–the only prenatal tests that can definitively diagnose fetal genetic disorders like Down Syndrome–out of fears of miscarriage. No one has studied this question. But the number is likely considerable.

And that’s unfortunate, because the risk of miscarriage from these tests has been wildly overblown.

 

AMNIO and CVS are the only tests that can definitively diagnose fetal genetic disorders…

yet many women shy away from these tests because they fear a miscarriage.


Amnio and CVS: The Basics

Let’s back up a second to review how amnio and CVS work. Amnio and CVS involve using a needle to pull out a small amount of amniotic fluid (amnio) or cells from the placental villi (CVS); A laboratory technician then analyzes the DNA in these samples.

Because both procedures require inserting a needle into the uterus, they carry a small risk of causing an infection, which can lead to miscarriage.


How often do these tests cause miscarriage?

Reputable sources like the Center for Disease Control state the risk of miscarriage as about 1 in 100 for CVS and 1 in 200 for amnio.

But these estimates are outdated. They derive from studies conducted in the 1980–before the routine use of ultrasound during these tests, a practice widely viewed as having dramatically lowered the risk of miscarriage. In other words, the older estimates are almost surely overblown.

Studies since the 1980s find a much lower risk of miscarriage from these procedures, one too small to be accurately estimated and often not even statistically distinguishable from zero. For instance, a large prospective Danish study of over 140,000 pregnancies found no impact on miscarriage risk. And a comprehensive meta-analysis of 21 studies conducted in the 2000s found a small non-significant post-procedure bump in the chances of miscarriage: about 1 in 1000 for amnio, and 1 in 500 for CVS.

 

The chances of miscarriage after AMNIO and CVS are Small: 

about 1 in 1000 for amnio, and about 1 in 500 for CVS.


Does this difference in risk matter?

This is a personal question. For some, the answer is “No” – any additional chance of miscarriage whether 1 in 100 or 1 in 10,000, is too much to bear. That’s totally understandable.

But for me personally, and for lots of other women, an added a 1 in 100 chance of miscarriage is too high. But a 1 in 500 chance? For me, that was worth it for the additional information and peace of mind.


Postscript Note:

These tests have come a long way. With recent advances in genetic knowledge and analysis, amnio and CVS can now detect a much wider spectrum of genetic disorders than they could just a few years earlier.  This is a benefit relevant to all expecting parents regardless of their age.

Learn more about the benefits of diagnostic genetic tests in the second post in this series on amnio and CVS.

amniocentesis risks

Or check out our Complete Guide to Prenatal Testing ebook.

 

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About Amy

Amy Kiefer is a researcher by training, and earned her Ph.D. from the University of Michigan. She currently lives in the Bay Area with her husband and three children where she writes about fertility, pregnancy, and breastfeeding. Check out her blog, expectingscience.com, for more great evidence-based pregnancy and parenting info.

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