06 January 2009

Prenatal test tied to birthmarks

A test performed in early pregnancy to check for genetic defects in the foetus appears to be linked to increased chances that the baby will be born with a birthmark.

A test performed in early pregnancy to check for genetic defects such as Down's syndrome in the foetus appears to be linked to increased chances that the baby will be born with a birthmark, or "infantile haemangioma," researchers report.

Chorionic villus sampling or CVS involves using a needle to collect samples of the embryonic structure that goes on to form the placenta. The process can be performed as early as 10 weeks into pregnancy, and provides cells of foetal origin that can be examined for chromosomal abnormalities.

Because several reports published in the 1990s suggested that there were occasional foetal effects from CVS, Dr Lewis B. Holmes reviewed published studies to see if the procedure might be linked to infantile haemangioma and possibly limb defects.

"Only a few studies have been conducted on the occurrence of haemangioma in CVS-exposed infants," Holmes, of Massachusetts General Hospital for Children, Boston, emphasises in his article in the Journal of Craniofacial Surgery.

In one study, Holmes reports, researchers found "cavernous or strawberry haemangioma" 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, haemangioma was 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 haemangioma.

Higher risk of birth defects
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.

One large study, Holmes reports, found that the underdevelopment or absence of any two fingers occurred in 1 of 3 372 CVS-exposed infants compared to 1 of 53 751 unexposed infants.

Furthermore, a multi-state study from 1988 to 1992 showed that limb defects were "six times more common in CVS-exposed infants in comparison to the unexposed," he notes.

Nonetheless, because CVS detects serious genetic diseases like Down's syndrome, "the benefits of knowing the test results could outweigh the possible risk of haemangioma or other abnormalities," the editor-in-chief of the journal points out in a written statement.

SOURCE: Journal of Craniofacial Surgery, December 2008.

(Reuters Health, January 2009)

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