August 31, 2006

Risk of prenatal CVS same as amniocentesis: study

LOS ANGELES (Reuters) - The risk of miscarriage after
undergoing chorionic villus sampling, or CVS, to detect birth
defects is lower than previously thought and essentially
carries the same risk than the more commonly used
amniocentesis, according to new research.

The findings, although based on a fairly small sample of
cases, are important because most women prefer prenatal
screening as early as possible in pregnancy, and CVS is
performed about six weeks earlier than amniocentesis.

Both procedures carry a small risk of miscarriage, but the
study found that the risk attributable to CVS is the same as
the risk of 1 in 370 seen with amniocentesis when adjusting for
the earlier gestational age of the CVS procedure.

Amniocentesis, which involves inserting a needle through
the abdomen into the uterus to withdraw amniotic fluid, is
performed early in the second trimester at 16 to 20 weeks of

CVS involves collecting a small sample of placenta cells
from the lining of the uterus either by inserting a slender
needle through the abdomen or by inserting a thin plastic tube
through the vagina into the placenta. It is done in the first
trimester, between 10 and 12 weeks gestation.

Based on earlier research, women have been counseled that
the miscarriage risk from CVS is greater than with

Researchers at the University of California at San
Francisco studied data from 1983 to 2003 on nearly 10,000 CVS
and 31,000 amniocentesis procedures performed at a single
prenatal diagnostic center.

The study, published in the September issue of the journal
Obstetrics & Gynecology, found that the overall pregnancy loss
rate over the 20-year period was 3.12 percent for CVS and 0.83
percent for amniocentesis.

When the researchers controlled for gestational age,
maternal age, and indication for the procedure, they found no
difference between losses from CVS or amniocentesis.

And, when examined in five-year intervals, the pregnancy
loss rate from CVS dropped to 1.93 percent in the last
five-year period of the study.

They suggested that the miscarriage rate from CVS may have
decreased as doctors became increasingly proficient at
performing the procedure.