Study touts early Down syndrome tests
Bulletin for mothers-to-be: A new study of nearly 40,000 pregnant women found that the best time to screen a fetus for Down syndrome is at 11 weeks into a pregnancy, rather than in the second trimester.
For well over a decade, the official standard of care has been to perform the blood tests to screen for a possible chromosomal problem at about 15 or 16 weeks into a pregnancy. But in the past several years, Boston's major hospitals and other centers with advanced obstetric care have been offering earlier screens, combined with an early ultrasound scan that can also catch signs of trouble.
Now, the federally funded, carefully controlled study, published in today's New England Journal of Medicine, is likely to spread the early screens far wider and persuade more insurers to pay for them, the study's authors say.
With the study's size and clout, it surely ''will come to the attention of the average practicing obstetrician, who's going to need to accommodate some of these advances," said one of the study's authors, Dr. Diana Bianchi of Tufts-New England Medical Center's Floating Hospital. Pregnancy is an anxious time for many women; the earlier they get word that their baby appears healthy, the better.
Tests at 11 weeks, counting from the last menstrual period, provide reassurance to the vast majority of women. When the results suggest a high risk of chromosome problems, the woman may choose to have an invasive test such as an amniocentesis, which carries a slight risk of miscarriage, to find out for sure.
If the fetus's chromosomes are found to be abnormal, some women may then choose to end the pregnancy -- and earlier abortions are far safer than later ones. Other women use the extra time to prepare for a child that may have problems.
Rough estimates hold that only about 15 percent of the women who are screened get tested in the first trimester, said Dr. Mary D'Alton of Columbia University, another of the study's researchers. Many women choose not to get tested at all.
Well before this latest study's results, other studies and clinical practice had made clear that first-trimester screening, in the right hands, was an excellent option.
Blue Cross and Blue Shield of Massachusetts recently began covering the early screens. The American College of Obstetricians and Gynecologists has also endorsed them under the right conditions.
''The data have been there for a long time," said Dr. Allan Nadel, an obstetrical ultrasound specialist at Massachusetts General Hospital, which has offered the early tests since 2002. ''The responsible bodies have given it their imprimatur; and it's just a question that it doesn't seem to be something that people are taking up properly."
Part of the lag seems to stem from a skills gap. The ultrasound scan involved in the early screening, which checks the fetus's neck area for an abnormal thickening, requires the technician to find minute differences that are tricky to detect. Errors can have dire consequences: a diagnosis missed, or a false diagnosis leading to a needless invasive procedure that can result in miscarriage.
The study's researchers cautioned that women who seek the early screening should inquire whether the providers who perform it have been properly trained and maintain a quality assurance program.
Patients are often in no rush to have their first obstetrician's appointment, said Dr. Fergal Malone of Ireland's Royal College of Surgeons, the first author of the study.
''We're trying to get the message out there that people should show up as early as possible for prenatal care," Malone said.
The study, which is known by the acronym FASTER, for First- and Second-Trimester Evaluation of Risk, found that the blood tests and ultrasound, performed at 11 weeks, detected 87 percent of the cases of Down syndrome.
An accompanying editorial in the New England Journal of Medicine summed up the study's results: ''First-trimester screening is thus clearly superior to screening in the second trimester."
Carey Goldberg can be reached at Goldberg@globe.com 