Here is what the research found.
Risk of the second child being born with autism is 50% high, a new study by the US Centers for Disease Control and Prevention (CDC) revealed.
However, waiting for too long like four years is just as risky, researchers warn as it can lead to fertility issues, the Daily Mail reported.
Women require close to 18 months to get to a healthy state so they have the level of nutrients to nourish a baby they are carrying. Researchers recommend sticking to this time frame to avoid low birth weight, placental abruption and premature births, the report stated.
For the study, researchers analysed the data from 356 children with autism, 600 with developmental disorders and 524 children with no disorders. Based on this information they discovered that if the "birth spacing" was too long or short it was "uniquely" connected with autism.
"These findings support existing guidelines on pregnancy spacing and further highlight the association between autism and pregnancy health," lead author Dr. Laura Schieve of CDC told the Daily Mail. Adding, "Couples thinking about getting pregnant should discuss pregnancy planning with a trusted doctor or healthcare provider."
The study was originally published in the journal Autism Research.