Close birth spacing may raise autism risk

Children born less than two years after their siblings were considerably more likely to have an autism diagnosis compared to those born after at least three years.

The sooner the second child was conceived the greater the likelihood of that child later being diagnosed with autism. The effect was found for parents of all ages, decreasing the chance that it was older parents and not the birth spacing behind the higher risk.

“That was pretty shocking to us, to be honest,” said senior author Peter Bearman of Columbia University in New York. The researchers took into account other risk factors for autism and 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. Still, he said more studies are needed to confirm the birth spacing link.

Closely spaced births are increasing in the US because women are delaying childbirth and because of unplanned pregnancies. Government data show the number of closely spaced births—where babies are less than two years apart—is rising, from 11 per cent of all births in 1995 to 18 per cent in 2002.

The study comes just days after a new report further tarnished a British researcher’s 1998 paper linking vaccines to autism, this time calling the paper a fraud based on altered facts.

Bearman contrasted the new research to what he called the “junk science” behind the notion that vaccines cause autism.