New research may change the way doctors screen pregnant women for Down syndrome and other genetic disorders.

A test that can detect the disorders in the first trimester of pregnancy has proved highly accurate in study of more than 38,000 pregnant women at 15 U.S. research centers. The results are published in Thursday's issue of the New England Journal of Medicine.

Down syndrome is one of the leading causes of mental retardation and birth defects, found in one in 660 pregnancies. Any woman can have a baby with Down syndrome, regardless of her age, race, health, economic status or family history.

Christina O'Donnell is expecting her third child in March. Like all pregnant women, she hopes for a healthy baby, reported WCVB-TV in Boston.

But unlike most women who get screened for Down syndrome and other potential risks in their second trimester, O'Donnell knew just 11 weeks into her pregnancy that her baby's risk was low.

"It was important for me to know, and I wanted to know as soon as I could," O'Donnell said.

In the new screening test, a sample of the mother's blood is analyzed for the level of a protein and hormone, and an ultrasound or sonogram picture is analyzed for the thickness of skin on the back of the baby's neck. Results are available within five days.

The current standard screening is a blood test performed in the second trimester of pregnancy that has an 81 percent detection rate, said Dr. Diana Bianchi, of Tufts New England Medical Center.

Screening in the first trimester detected 87 percent of Down syndrome babies, and combined screening in the first and second trimesters resulted in 95 percent detection.

"The combined is the best route if you want to have the safest combination of tests," Bianchi said.

So far, 1,600 physicians and sonographers nationwide have undergone training to conduct the new test.

The findings mean women who used to rely on invasive and potentially dangerous procedures like amniocentesis no longer have to put their unborn child at risk.

"It's a no-brainer to do that over doing something that could potentially harm your baby," O'Donnell said.

First-trimester testing can also detect congenital heart disease and other genetic disorders earlier. Critics say the information may lead to more parents deciding to abort fetuses with potential problems.

Doctors say past studies show the information will give parents a chance to adjust and physicians a chance to address any health concerns sooner.

• Study Abstract