There is already enough apprehension for a woman during pregnancy, especially if she is 35 or older and expecting for the first time. Dr. Sherman Elias is hoping to help eliminate some of the worries.
Elias and colleagues at the University of Illinois at Chicago were recently awarded a $3.1 million federal grant from the National Institutes of Health to participate in the next phase of a national research study exploring whether a simple blood test might be an effective way to identify birth defects.
Currently, women can discover any such genetic threats to their babies as Down syndrome, sickle-cell anemia and cystic fibrosis only by undergoing the more invasive prenatal screening tests amniocentesis and chorionic villus sampling (CVS).
In amniocentesis, the doctor removes a sample of amnio fluid, which surrounds the fetus and contains cells shed by the fetus. The fluid is removed by a needle inserted through the abdomen. Ultrasound imaging is used to guide the needle and avoid harming the baby. Amniocentesis is typically done between the 17th and 19th week.
The CVS screening can be performed earlier, usually during the 12th or 13th week. Using an ultrasound-guided needle inserted in the lower abdominal wall or a catheter that goes through the cervix, the physician will remove a sample of the placenta for lab analysis.
Both tests have their supporters in the medical community, though amniocentesis is more popular with patients. One major reason is the widely circulated myth that CVS puts babies at higher risk for limb deformation and missing fingers. In any case, both tests increase risk of miscarriage by somewhere between .3 percent and 1 percent, depending on the procedure and the experience of the physician performing it. The risk of miscarriage during the first 12 weeks is 3 percent for the typical woman.
“We have done a lot of work in our group and at other medical centers around the country to develop a blood test that is no risk at all to the pregnancy,” said Elias, chief of the obstetrics and gynecology department at UIC.
The technology is already available to locate and evaluate abnormal DNA, said Elias. Now it is a matter of proving the blood test’s reliability. What excites doctors such as Elias is how the fetal cells circulating in a mother’s bloodstream can now be more accurately isolated and analyzed for DNA irregularities. All of this lab wizardry promises to spare women the needle or catheter used in amniocentesis and CVS.
“We need to study several thousand patients to get a sufficient number of abnormal readings for research purposes,” said Elias. Even so, this blood test is likely to be available within three years to help women make decisions. It may be the test is used even sooner for some birth defects.
Mark I. Evans, professor and chairman of ob-gyn at Medical Center of Pennsylvania at Hahnemann University in Philadelphia, said the blood test will be of a screening type that it will take a woman from moderate risk to low risk. Evans said he still prefers CVS because it gives a woman more privacy because it is done earlier. Research has supported the hope that the blood test can ultimately replace amniocentesis and CVS. A recent article in the British professional journal Lancetreported a high level of predictive value for the blood test. The ongoing NIH study is expected to report more of the same.
Elias says he anticipates insurance carriers, who usually cover amnio and CVS in woman older than 35, will routinely cover the blood test once the U.S. Food and Drug Administration approves its use. In any case, lots of angst figures to fade. “All couples worry about birth defects,” he said. “Prenatal screening can greatly reduce anxiety.”
Another plus: The simple blood test could be more commonly used in pregnant women 30 and younger. The American College of Obstetricians and Gynecologists reports that a 35-year-old women faces a 1-in-200 risk of bearing a child with chromosomal abnormalities, a risk that rapidly increases until the 45-year-old confronts a 1-in-20 risk. The 25-year-old expectant mother has a 1-in-500 chance, yet it turns out women between 25 and 35 have the greatest number of babies with birth problems.
“It is not a trivial issue to address birth defects in younger women,” said Elias. Elias does have one serious concern. Because prenatal testing promises to become less risky and invasive by mid-decade, he frets that some couples will feel pressured into prenatal genetic screening when they actually prefer not to know anything about the baby until he or she is delivered.
If the risk disappears — and things are heading that way — said Elias, he doesn’t want any couple to feel forced into it.
“Many couples say prenatal diagnosis isn’t for them,” says Elias. “That’s OK with me, but I want all patients to know their options.”
