Common Prenatal Tests Carry Low Miscarriage Risk

Two standard prenatal diagnostic tests -- amniocentesis and chorionic villus sampling (CVS) -- both carry a low risk of miscarriage, a U.S. study finds.

The tests are done to identify fetal genetic or chromosomal abnormalities.

Researchers at the University of California, San Francisco, examined data from 9,886 CVS and 30,893 amniocentesis procedures performed at UCSF Medical Center from 1983 to 2003. The miscarriage rate for women having CVS was 3.12 percent, compared with a 0.83 percent rate for amniocentesis.

The study also found that the miscarriage risk associated with both CVS amniocentesis declined over the 20 years covered in the study. And when the researchers factored in gestational age and maternal age, they found no differences between the miscarriages from either CVS or amniocentesis.

"This is a significant finding for use as information in both patient counseling and in establishing widespread prenatal diagnostic and screening programs," study co-author Dr. Mary E. Norton, medical director of the Prenatal Diagnostic Center at UCSF Medical Center, said in a prepared statement.

It was previously believed that CVS had a higher miscarriage risk than amniocentesis.

"If there is no difference in risk associated with CVS and amniocentesis, women are more likely to choose CVS because information can be provided much sooner," said Norton, who is also an associate clinical professor in the department of obstetrics, gynecology and reproductive sciences.

CVS is a biopsy procedure that involves the removal of a small piece of tissue from the placenta. Amniocentesis involves collecting a sample of amniotic fluid by inserting a hollow needle through the abdominal wall.

The findings were published in the September issue of the journal Obstetrics and Gynecology.

More information

The Nemours Foundation has more about prenatal tests.