NEW YORK-It’s the baby’s first portrait, a shadowy gray-and-black image in the second trimester.
But though ultrasound fetal scans are ubiquitous, it’s not clear that they should be routine. Parents are usually comforted by them, yet many obstetricians see no good medical reason for screening every fetus.
In Europe, however, ob-gyns see every reason for doing so, and now they’re backed up by a huge study. The Europeans say they detect fetal anomalies at a higher rate than U.S. doctors because, quite simply, they are better sonographers. And they have gotten better, they add, because they do many more scans. A new U.S. study also suggests that screening may be more useful than the American College of Obstetricians and Gynecologists and others have claimed.
The U.S. dogma emerges from the Routine Antenatal Diagnostic Imaging with Ultrasound Study (RADIUS), a 1993 NIH-sponsored trial of 15,151 low-risk pregnant women that found screening detected just 16.6% of 187 major fetal anomalies before 24 weeks of gestation and 34.8% before delivery. The study concluded that screening doesn’t improve perinatal outcome, compared with scanning based on clinical judgment.
But in a new Medical University of South Carolina study, 75% of major fetal anomalies were detected in 2,031 low- and high-risk women screened in weeks 15 to 22 of pregnancy, Dr. J. Peter Van Dorsten told an ob-gyn meeting in Victoria, B.C. They included cleft lip, clubfoot, dwarfism, gastroschisis, anencephaly, hydronephrosis, and spina bifida.
In the Eurofetus Project’s preliminary results, presented at a New York Academy of Sciences meeting here on prenatal screening, ultrasound detected 61.4% of fetal anomalies in 3,685 babies who were born with abnormalities at 60 European hospitals-twice RADIUS’ rate. The low false-positive rate in the study of 200,000 women was 18%, half of which were corrected on a second sonogram.
Still Harvard’s Dr. Fredric Frigoletto, a co-author of RADIUS, says “not a shred of scientific evidence” has changed his mind. He’s unimpressed by the South Carolina data.
“Ultrasound is the most powerful diagnostic tool in obstetrics,” he says, “but it doesn’t pass muster as a screening test because it’s too costly and not universally available.” He and others also cite inadequate sensitivity, false positives, and lack of physician expertise. They estimate the extra cost of screening all pregnant women in the U.S. at $200 a scan would be more than $1 billion annually.
They say routine screening misses some defects, such as cerebral palsy, and doesn’t detect some neurologic and GI anomalies in time for pregnancy termination. The false-positive rate hasn’t been adequately assessed, says Dr. Nicholas Wald of the University of London, who questions the value of informing parents of uncorrectable or minor anomalies.
But at the two recent meetings, many participants favored bringing routine screening to the U.S. Cornell’s Dr. Frank Chervenak believes every pregnant woman should be offered screening because anomalies occur in 2% to 3% of all pregnancies. Proponents say that for many serious anomalies there are no clinical indications, and failure to do what Brussels ob-gyn Salvator Levi calls a “harmless, painless” scan can become the linchpin of a lawsuit.
Prenatal diagnosis of a defect allows the patient to elect an abortion or arrange for delivery at a tertiary-care center. If a pregnant woman is not scanned, says Columbia’s Dr. Ilan Timor, the fetus is neglected. He recommends two scans, a transvaginal probe at 14 to 16 weeks for an 80% to 85% detection rate and a transabdominal scan at 20 to 22 weeks for a rate of 95%.
In Europe prenatal screening is rarely omitted, and there’s no debate over insurance reimbursement, no managed-care squeeze. Pregnant women receive at least one scan in Britain, two in Germany, three in France, with insurers in each nation paying an average $40 per exam.
Much of the U.S. controversy revolves around scan sensitivity and physician training, which vary widely. Dr. John Hobbins of the University of Colorado says most ob-gyn residencies don’t provide adequate training in ultrasound. Primary-care physicians identify only about 10% of defects, vs. 50% at tertiary-care centers, he says. But even in selective screening of high-risk patients, many malformations are missed. And in managed care, primary-care physicians aren’t encouraged to refer to specialists, he adds.
Ultrasound technology has become more sensitive, but detection is still operator-dependent, says Dr. Richard Berkowitz of New York’s Mount Sinai. The person who holds the probe is important, agrees Dr. Frigoletto. In the U.S. that person may be a technician, whereas in Europe, it’s more likely to be an ob-gyn or radiologist.
Ultrasound for GI defects has a sensitivity of 14% to 86%, says Cornell’s Dr. Daniel Skupski, depending on the examiner’s skill and the defect. If routine screens were done at centers with special expertise, false positives would decline, he believes.
Fetal heart defects also do better in experienced hands, says Dr. Greggory DeVore of Pasadena’s Genetics Institute. An examiner trained to interpret a four-chamber view identified 55% of heart anomalies, vs. 5.3% found by inexperienced examiners.
While the debate goes on, women are siding with scans. At Harvard Pilgrim Health Care, pregnant women expect one, and they averaged 2.43 scans in 1996, says Dr. Elizabeth Buechler. -Elsie Rosner
NEW YORK-It’s the baby’s first portrait, a shadowy gray-and-black image in the second trimester.
