Closely-spaced pregnancies are linked to a higher risk of autism in the second-born child, according to a new study involving more than 600,000 sibling pairs.
The study, which the journal Pediatrics published online Monday, showed that the risk of the second child being diagnosed with autism was significantly increased if there were fewer than 36 months between the pregnancies.
The highest risk was associated with pregnancies less than a year apart, according to Keely Cheslack-Postava, PhD, and colleagues at Columbia University in New York City.
The study looked at more than 660,000 second-born children in California between 1992 to 2002. It measured the time the second child was conceived relative to the first child, and then looked at autism diagnosis of the second sibling.
However, researchers cautioned that additional studies need to be done to confirm the findings.
Still, one of the researchers, Peter Bearman, a sociologist at Columbia University in New York, said "we see this really profound association" that remained when other factors, such as the age of the parents were looked at.
"We don't know what causes this," he said.
- Editor: Deng Shasha（Xinhuanet）
