Prenatal Assurance

It used to be that most children with Down syndrome, the genetic abnormality that leads to physical deformity and mental retardation, were born to women age 35 and older. For that reason, many older expectant mothers now have amniocentesis to see whether the baby’s genes bear the telltale defects associated with the ailment. The result is that fully 80% of victims today — in the U.S. at least — are born to mothers 35 and younger. These women tend to avoid amniocentesis because for them the risk of bearing kids with Down syndrome is significantly lower than the risk from the testing procedure itself, which can cause miscarriage.

That is why a report in the New England Journal of Medicine is so & significant: doctors in Maine and Rhode Island have shown that by using three blood tests — for substances called alpha-fetoprotein, unconjugated estriol and chorionic gonadotrophin — they could determine which young mothers were at highest risk for bearing afflicted children. The first test alone predicts Down syndrome correctly 35% of the time, but all three together boosted the rate to nearly 60%, thus targeting women who are most likely to benefit from amnio.