In a recent study it has been reported that pregnancies with less than 36 months gap leads to a higher risk of autism in the second sibling.
The study involved more than 600,000 second children born in California between 1992 to 2002.
Keely Cheslack-Postava and colleagues at Columbia University in New York City pointed out that mothers with pregnancies less than a year apart were under a higher risk, reports English.News.Cn.
"We see this really profound association, we don't know what causes this," said Peter Bearman, of the Columbia University.
However, researchers added that additional studies should to be done before confirming the findings.
The report was published in the journal Pediatrics.