Test for birth defects may cause birth defects

Damned if you do…

I read this report back before Christmas on the risks related to chorionic villus sampling (CVS), a common prenatal diagnostic test for Down’s syndrome, but I didn’t really take it in.

A study by Dr. Lewis B. Holmes of Massachusetts General Hospital for Children has reviewed past research on the possible link between CVS and birth defects and indicated that CVS may increase the risk of that the baby will be born with a birthmark, or “infantile hemangioma” or even limb defects.

According to this report from Reuters:

“In one study, Holmes reports, researchers found “cavernous or strawberry hemangiomas” in 12 of 95 (12.6 percent) CVS-exposed infants compared with 3 of 87 (3.4 percent) infants who had been exposed to amniocentesis, which is typically performed later in pregnancy.

In another study, hemangiomas were seen in 21.1 percent in 578 CVS-exposed infants versus 7.4 percent in 445 amniocentesis-exposed infants. Some babies in the CVS group, but none in the amniocentesis group, had multiple hemangiomas.

Holmes also looked at the evidence for an association between CVS and birth defects involving the limbs, especially the fingers, and found some “clear” correlations. The evidence suggests that these risks are greater when CVS is performed earlier in pregnancy, such as at 8 to 9 weeks gestation.”

The Editor-in-Chief of the Journal of Craniofacial Surgery points out that “CVS is generally done for prenatal detection of serious genetic diseases like Down’s syndrome in pregnancies at high risk” and that “the benefits of knowing the test results could outweigh the possible risk of hemangiomas or other abnormalities”.

Which is probably true, but the risk of birth defects should also be factored into any cost/benefit analysis of diagnostic testing. I certainly don’t remember it being mentioned when we were preparing for our CVS test.