For decades, pregnant women 35 and older have routinely been tested for chromosomal abnormalities that might affect their fetus, most notably Down syndrome. Younger women were tested much less often because the risk of birth defects was low and invasive procedures like amniocentesis carried risks of their own.
But now the American College of Obstetricians and Gynecologists is recommending Down syndrome screening for all pregnant women, regardless of their age.
The change was prompted in part by new, less invasive screening techniques, including an ultrasound exam that helps assess risk as early as 11 weeks into a pregnancy — though not as accurately as the invasive procedures, amniocentesis and chorionic villus sampling.
But the new recommendations also address a demographic fact of life: while older women are at greater individual risk of conceiving a child with Down syndrome, most babies with the disorder are born to young women, simply because they give birth in far greater numbers.
“It’s been pretty much ingrained in obstetricians’ minds that 35 is the cutoff age,” said Dr. Deborah A. Driscoll, chairwoman of the obstetrics department at the University of Pennsylvania and a lead author of the new recommendations. “We’re trying to move away from that.
“The take-home message,” Dr. Driscoll continued, “is that all women, regardless of age, should be offered Down syndrome screening, and any woman should then have the option of diagnostic testing.”
Down syndrome is the most common chromosomal abnormality, affecting 1 in 800 live births. Children with the syndrome, who are born with an extra chromosome, display unusual facial features, suffer from moderate to severe mental retardation, and are at high risk for congenital heart defects and other health problems.
The risk of conceiving a child with a chromosomal abnormality does increase with age. For Down syndrome, the risk is 1 in 1,250 at age 25 but 1 in 106 at age 40. [. . . . Snip] NYTimes