(Reuters Health) - As many as one in 10 U.S. children may have fetal alcohol spectrum disorders, far more than previously thought, a new study of first graders suggests.

Fetal alcohol spectrum disorder is an umbrella term for a range of physical, psychological, behavioral and cognitive problems that can develop in children whose mothers drink during pregnancy. The most severe form, fetal alcohol syndrome, can cause stunted growth, learning disabilities, bone and joint deformities, heart defects, and hyperactivity.

Even though early diagnosis and treatment can sometimes reduce the severity of fetal alcohol spectrum disorders, the vast majority of cases remain undiagnosed. Prior estimates, which suggested that only 1 in 100 kids is affected, may have grossly underestimated the problem, researchers note in JAMA.

“The earlier that interventions are initiated, the more effective they are likely to be - especially during the early years when there is still relative plasticity of the brain,” said Christina Chambers of the University of California San Diego School of Medicine and Rady Children’s Hospital San Diego, who co-led the study.

“There is no cure for fetal alcohol spectrum disorders, but there are definitely intervention strategies that have been demonstrated to help,” Chambers said by email.

The current study focused on 13,146 first-grade students in four communities in the Rocky Mountain, Midwestern, Southeastern and Pacific Southwestern regions of the U.S. This included 6,054 children who were screened for growth, development, or both, as well as 585 children who were randomly selected to receive detailed clinical exams for physical abnormalities linked to fetal alcohol spectrum disorder.

Overall, researchers identified 222 cases of fetal alcohol spectrum disorders, including 27 severe cases that met the criteria for fetal alcohol syndrome.

Only two of these kids had already been diagnosed with fetal alcohol spectrum disorders, even though many of their parents and guardians were aware that their children faced learning and behavioral challenges.

For a conservative estimate of the extent of the problem, the researchers assumed that no additional cases would be found in first graders who weren’t included in the study. On this basis, the proportion of kids with fetal alcohol spectrum disorders ranged from a low of 1.1 percent in the Midwestern community to a high of 5 percent in the Rocky Mountain group.

When researchers ran the numbers again, this time assuming that the rates found in the study reflected the rates in the communities, the condition appeared more common.

Now, the proportion of kids with fetal alcohol spectrum disorders ranged from a low of 3.1 percent in the Southeastern group to 9.9 percent for the Rocky Mountain community.

One limitation of the study is that children who received permission from their parents to participate might have differed from kids who didn’t, in ways that influenced whether they might have fetal alcohol spectrum disorders, the authors note. It’s also possible that results from these four communities might not reflect the prevalence of fetal alcohol spectrum disorders elsewhere.

Still, the results suggest that the fetal alcohol spectrum disorders are widespread, and that many women may be unaware of the risk, said Dr. Svetlana Popova, co-author of an accompanying editorial and a researcher at the Center for Addiction and Mental Health at the University of Toronto.

“It is not safe to drink any amount or type of alcohol, at any time during pregnancy, when trying to get pregnant, or when breastfeeding,” Popova said by email. “Although it has been shown that a high blood alcohol concentration is the most harmful to a developing fetus, which is achieved by drinking a large amount of alcohol over a short period of time, low amounts have also been shown to have negative consequences.”

SOURCES: bit.ly/2FQWRMd and bit.ly/2FShp72 JAMA, online February 6, 2018.