Over the last ten years, new technology has improved the methods of detection of fetal abnormalities, including Down syndrome. While there are ways to diagnose Down syndrome by obtaining fetal tissue samples, it would not be feasible to examine every pregnancy this way. Besides increasing the health care costs, these methods do carry some risk to the fetus. As a result, screening tests are available now to try and identify high risk pregnancies where further diagnostic testing may be appropriate.

When we talk about diagnostic versus screening, there is a difference. In diagnostic tests, a positive result very likely means the patient has the disease or condition. In screening tests, the goal is to estimate the risk of the patient having the disease or condition. Diagnostic tests tend to be more expensive and require a more elaborate procedure. Screening tests are quick and easy to do and tend to have a higher degree of false positives and false negatives.

Methodist Medical Group Perinatology under the guidance of Dr. Charles Egley can now offer a first trimester screening test that reliably identifies fetuses likely to be born with Down syndrome. This new test provides expectant women with information much earlier in their pregnancy. Methodist is the first in Illinois outside of Cook County to offer the first trimester diagnosis.

A recent study of 38,000 women in the U.S. found that the screening method can pinpoint many fetuses with the common genetic disorder 11 weeks after conception. The test combines a blood test with an ultrasound exam.

Screening women before the second trimester allows expectant mothers additional time to prepare emotionally for their child’s condition, and allows earlier reassurance to those whose babies are healthy, avoiding weeks of anxiety.

The eight-year study was funded by the American College of Obstetricians and Gynecologists at cost of $15 million.

Down syndrome is the most common major chromosomal abnormality, occurring in about 5,000 babies born each year in the U.S. The syndrome results when a baby has three, rather than two, copies of the 21st chromosome, causing distinctive physical features, developmental problems and an increased risk of a variety of health problems that usually shorten the child’s life span.

At present, women who are especially at high risk due to family history or age are offered a blood test at about 16 weeks into a pregnancy. Women who test positive can then undergo a procedure called amniocentesis to confirm the diagnosis.

The new earlier screening test uses an ultrasound called the nuchal translucency to measure the thickness of the skin on the back of the fetus’s neck and a blood test to measure levels of a protein and a specific hormone.

A study comparing the techniques involved 38,167 women at 15 U.S. centers, who underwent both procedures and then were followed to see which fetuses had Down syndrome

The first trimester approach identified 87 percent of Down babies when used at 11 weeks, while the later test identified 81 percent. The two tests together detected 95 percent of the cases.

Those with the highest risk of having a Down syndrome baby are those who have already had a baby with the syndrome, mothers of fathers who have a rearrangement involving chromosome 21, and mothers over 35 years old. The risk of Down syndrome increases with age.

The decision to screen for Down syndrome or other abnormalities is personal. For many women, earlier screening will provide welcome peace of mind about their baby’s health. For others, early detection can offer precious time to prepare for the challenges that may lie ahead.

Dr. Egley is board-certified in both Obstetrics-Gynecology and Maternal-Fetal Medicine – the management of high-risk pregnancies. He provides complete prenatal care for women with complicated pregnancies.