A preliminary study, looking at half a million children in California, has identified a possible link between birth spacing and autism.
Children born within two years of the first born were more likely to have autism than siblings born three or more years later. This was true for children of parents of all ages, causing researchers to wonder if child spacing makes a bigger impact on autism rates than parental age.
Senior author of the study, Peter Bearman of Columbia University in New York, was surprised by the results; even when they factored in other risk factors for autism, his team still saw the effect of birth spacing.
“No matter what we did, whether we were looking at autism severity, looking at age, or looking at all the various dimensions we could think of, we couldn’t get rid of this finding,” Bearman said. He also pointed out that science is “slow and proceeds in steps.” And that more research needs to be done.
The study, published today in Pediatrics, comes on the heels of a big week in autism news: The British scientist who claimed a connection between vaccinations and autism has been accused of publishing “junk science” and entirely discredited by the medical community.
It is estimated that about 1-100 children are on the autism spectrum. The rate of autism was under 1 percent for all children in the study. Siblings born soon after the firstborn were more likely to have autism but the rate was still under 1%. Women are having babies closer together more now than in recent history. In 1995, 11 percent of babies were born less than two years apart. Now, 18% are. This may be due to women waiting longer to have children or because of an increase in unplanned pregnancies.
The reasons for the increase in cases of autism with closely spaced kids is unclear. Maybe there’s some change in moms’ body chemistry– maybe mothers have decreased levels of folate? Perhaps parents are quicker to notice differences between children close in age and development. “And it could be a combination of effects, not a single explanation but a combination of dynamics,” Bearman said. He added that this shouldn’t alter family planning. The results are new and provocative, but they have yet to be confirmed. He does caution, however, against “junk science.”
photo:Frank de Kleine/flickr