Study Raises New Questions About Fetal Ultrasounds
A new study suggesting that first-trimester fetal ultrasound may contribute to the severity of autism symptoms heightens a dilemma facing obstetricians: How to halt the widespread overuse of fetal ultrasound without scaring women away from this important medical procedure.
The study, published Sept. 1 in the journal Autism Research, is the latest in a series of highly limited studies that raise questions about the safety of fetal ultrasound. Some research is based on animal studies—fetal chicks and rats, for instance—that may not be relevant to humans. The latest study, based on the medical histories of 2,644 families with autistic children, relies on parents’ reports of their ultrasound experiences rather than actual records.
Some medical leaders worry that these studies could produce an unwarranted backlash of the sort that occurred when now-debunked research allegedly tied childhood vaccinations to autism. Fetal ultrasound, which uses sound waves to gain a view inside the womb, can determine the date of conception, identify multiple fetuses and detect various abnormalities, among other valuable medical information. In a press release issued this month in response to the Autism Research study, the Society of Diagnostic Medical Sonography said pregnant women “should not avoid having medically necessary examinations using ultrasound during pregnancy based on this limited study.”
Fetal ultrasound is being used at ever-rising rates far beyond medical guidelines. In a low-risk pregnancy free of complications—or about 80% of all pregnancies—maternal-fetal experts recommend two fetal ultrasounds, the first around 12 weeks and the second around 20 weeks.
(snip)
Just as there’s no proof that fetal ultrasound causes harm, there’s no proof that it doesn’t. Nearly all research supporting its safety was conducted using equipment made before the mid-1990s, when the procedure produced about one-eighth the acoustic energy it is allowed to emit today and when fetal-ultrasound scanning was far less frequent. Since then, no major epidemiological studies have been conducted on fetal ultrasound.
(snip)
Ultrasound does create heat and exert force, however, and the premise of the new paper is that one or more such factors may be harmful early in pregnancy among fetuses with a genetic vulnerability to autism. Nearly everything about autism is controversial, including whether the dramatic spike in cases in recent decades reflects an increase in incidence or diagnosis. Among autism researchers, an increasingly accepted theory is that one or more environmental factors are triggering the condition in genetically vulnerable children.
(snip)
Because their latest article is based on data from a large pool of autistic children, with no non-autistic control group, the researchers set out to determine not what might have caused the condition but what might explain variations in severity. In particular they studied autistic children who had two known vulnerabilities to the condition—a genetic variation associated with autism, and male gender, which accounts for the vast majority of cases. They found significantly more-severe symptoms in 75 genetically vulnerable boys who underwent first-trimester ultrasound than in 38 who didn’t.
(snip)
Dr. Mourad and his co-authors argue that first-trimester ultrasound ought to be performed only when medically necessary. That may not sound radical. But many mothers-to-be are eager upon their first obstetric visit to catch a glimpse of the child forming inside them, and research suggests that many obstetricians gladly oblige. Medical indications for so early an ultrasound scan can include vaginal bleeding as well as pelvic pain, which can be a symptom of ectopic pregnancy. Of the two ultrasound scans that maternal-fetal experts recommend for the typical pregnancy, one—which provides early detection of Down syndrome—is performed late in the first trimester or early in the second.
http://www.wsj.com/articles/study-raises-new-questions-about-fetal-ultrasounds-1474312017
