Blood test screening reduces need for amniocentesis.

2003 DEC 4 - (NewsRx.com & NewsRx.net) -- Is simply being 35 or older enough reason for a pregnant woman to undergo amniocentesis to check for Down syndrome?

The older mothers-to-be are, the higher their risk of having babies with this fairly common birth defect. But nothing suddenly changes at the 35th birthday, and a 20-something can have a baby with Down syndrome, too.

Now growing evidence suggests that offering blood tests to screen every pregnant woman for the risk may be more effective than using today's standard age cutoffs for amniocentesis. This approach decreases unnecessary amnios by culling out which women of any age most need the invasive test, which is more accurate but occasionally causes miscarriage.

"Twenty years ago, the only way to identify women at risk was to offer amnio to those older than 35. That makes no sense any longer," says Rebecca Smith-Bindman, MD, of the University of California, San Francisco, who co-authored a large new study that supports screening-based instead of age-based decisions.

It's a policy that California has adopted, with a unique program that provides free amniocentesis for women whose screening tests determine they're at high risk.

Whether to have an amnio is an agonizing decision that more Americans are making as they increasingly postpone childbearing into their 30s and even 40s. For those who wouldn't consider abortion, prenatal diagnosis still is important because babies with Down syndrome - in which an extra chromosome causes mental retardation and other defects, often including heart problems - can need specialized care at delivery, which can affect hospital choice.

But women have a 1% chance of suffering a miscarriage from amniocentesis, the use of a needle to draw fluid from the amniotic sac, or from a similar invasive test called chorionic villus sampling. While it's a small risk, some women won't chance a test that could cost them a healthy baby.