BOSTON -- When an older woman becomes pregnant, there is always concern about birth defects. While there is a test that can provide some reassurance, that test carries its own small but real risk of miscarriage.

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Doctors Explain Screening Procedure RESOURCES Prenatal Diagnostic Center For Women: 35 Or Older At Delivery For Women: Under 35 At Delivery

NewsCenter 5's Heather Unruh reported that local doctors are now offering a new safer screening.

When Peg Drisko-Johnson first learned she was pregnant, she was over 35, which put her baby at greater risk of birth defects. She considered having a test called an amniocentesis, but she knew that carried a risk too -- a one in 200 risk of miscarriage.

"Any risk is too much risk when you are pregnant, I think you feel that way. And so for us, it was nice to have another option first," Drisko-Johnson said.

That option is called early-risk assessment or ERA. And its main component is a special ultrasound that can pick up problems as early as 11 weeks into the pregnancy.

"We're looking at the amount of fluid in the skin at the back of the neck. All babies have a little bit of fluid in that area, the more fluid, the greater the risk of a wide variety of problems -- the most important being down syndrome," Massachusetts General Hospital Dr. Allen Nadel said.

Unlike amniocentesis where a needle is inserted into the uterus, the ultrasound is non-invasive, posing no risk for the baby.

"In combination of the women's age, the image of the fluid and the blood test we think we get at least 80 percent and maybe as high as 90 percent of down syndrome," Nadel said.

ERA also provides sessions with a genetics counselor. Questions about family history can help guide blood tests that can also rule out disorders.

"For example, European people are at risk for cystic fibrosis, and so they can screen for that and African-Americans are at risk for sickle cell disease," Nadel said.

At age 37, Peg's risk of having a problem was about one in 150, but after ERA, she was told the risk was even lower. It was one in 1,500.

Baby Caroline was born in perfect health.

"I've told my friends about it who are older. I don't think women know it's an option yet, but they will now," Drisko-Johnson said.

Most insurance companies cover the cost of early risk assessment for women over 35. For those under 35, it is still available for a $325 out of pocket cost.