Knoxville (WVLT) - Gynecologists and obstetricians have long known, the older a woman is, the greater the risk of having a baby with Down Syndrome.
And so only mothers-to-be who were 35 and older were tested for this common birth defect.
Age 35 was always a somewhat arbitrary threshold for urging mothers-to-be to seek testing.
That age was chosen years ago, when doctors had little information about the risk of Down Syndrome and only one choice for detection.
About one in 800 babies has Down Syndrome, a condition where having an extra chromosome causes mental retardation, a characteristic broad, flat face and small head, and often, serious heart defects.
And the older the woman, the greater the risk, from one in 1,200 at age 25, to one in 300 at age 35.
Now, the American College of Obstetricians and Gynecologists is changing its Down Syndrome testing recommendation.
"That this is going to be the recommendation that every woman is offered first trimester screening. It's not going to be mandated or mandatory, but it will be offered to every woman regardless of age," the reason, OB-GYN Doctor Craig Myers says, is the test is far less invasive than the long-used amniocentesis.
He says it's a change that promises to decrease unnecessary amnios, giving mothers-to-be peace of mind without the ordeal, while also detecting Down Syndrome in moms who otherwise would have gone unchecked.
"However, now, we have the first trimester screening, which is offered a lot earlier between 11 and 13 weeks. It's a much more sensitive test and has a lower false-positive rate," says Dr. Myers.
Doctor Myers says this newest method gives a woman the numerical odds she's carrying a Down Syndrome fetus.
It's non-invasive and 91 to 97 percent accurate.
"There are two components to it, there's a blood test that looks at two specific screenings in the mother's blood, and it's combined with an ultrasound, an early ultrasound, that looks at the thickness behind the baby's neck," Dr. Myers explains.
The new guideline also says women of any age can choose to skip the screening and go straight for invasive testing, an approach that might appeal to couples with chromosomal defects in the family.
This first trimester testing is not just a question of whether to continue the pregnancy.
Prenatal diagnosis is also important for women who wouldn't consider abortion, because babies born with Down Syndrome may need specialized care at delivery that affects hospital selection.
But each test comes with pros and cons, and the new guideline advises doctors to discuss the best options with each individual patient.