Down syndrome screening becomes even more convenient

January 15, 2007
With recent news that all pregnant women – regardless of age – should be offered screening for Down syndrome, obstetricians in Wilmington, with the help of a local physician specializing in prenatal diagnosis, are preparing to make the test simpler, with quicker results.

The American College of Obstetricians and Gynecologists issued a statement on Jan. 2 that all women should consider advanced screening for the common birth defect. Previously, only women 35 and older were considered candidates for amniocentesis, the most common test.

Because amniocentesis carries a risk of miscarriage, only older women, more likely to give birth to Down syndrome babies, or those with high-risk pregnancies were considered for the test. Typically, the test was performed 16 to 18 weeks into a pregnancy.

The changes in policy on who should be offered Down syndrome screening are the result of advances in less invasive testing available beginning in first trimester of a pregnancy. Dr. Lydia Wright with Wilmington Maternal Fetal Medicine has been offering the advanced screening for more than a year.

The testing involves a combination of first-trimester ultrasound and first- and second-trimester blood work. The combined screening detects up to 92 percent of pregnancies with Down syndrome.

On the horizon are improvements in reporting of the screening results. Once available, patients who desire first-trimester screening may be able to receive preliminary results the same day as their ultrasound appointment. Many of those patients may follow with another blood test five weeks later, with an accuracy of more than 90 percent.

“This leaves patients feeling more reassured,” Dr. Wright said. “You don’t have to choose to have an invasive procedure and you don’t put your baby at risk.”

Because amniocentesis carries a small risk of miscarriage, only women considered to be at increased risk to give birth to a baby with a chromosome problem were offered the test. The original age 35 mark was chosen when doctors believed the risk for Down syndrome was close to the risk of amniocentesis.

In reality, more children with Down syndrome are born to mothers younger than 35, and the risk only gradually increases with age. A recent study has suggested that the risk of amniocentesis may be less than initially suspected and criteria for who should be offered the procedure will likely be revised.

Prenatal screening and diagnosis can be useful for some parents of children who may need specialized care during the pregnancy and at delivery. All prenatal diagnosis and screening tests are optional for pregnant women. It is each patient’s individual decision whether to pursue testing.

If you have a question about prenatal diagnostic testing, please contact your obstetrician, who can make a referral to a specialist. Genetic counselors are also available at Dr. Wright’s office at 815-5011.