Increased Autism Risk Found in Closely Spaced Pregnancies

An examination of California birth records found second-born children were more than three times.more likely to be diagnosed with autism if they were conceived within 12 months of the birth oftheir older sibling. The farther apart pregnancies were spaced, the lower the risk of autism.The study, "Closely Spaced Pregnancies Are Associated With Increased Odds of Autism in

California Sibling Births" published in the February 2011 issue of Pediatrics (published onlineJan. 10) examined the odds of autism among more than 660,000 second-born children.

 

Compared to children who were conceived more than three years after the birth of an older sibling, children conceived after an interpregnancy interval (IPI) of less than 12 months were over three times more likely to be diagnosed with autism. Children conceived after an IPI of 12 to 23 months were almost two times more likely to have been diagnosed with autism, and children

conceived after an IPI of 24 to 35 months were one and a quarter times more likely to have been diagnosed with autism.

One possible explanation for the increased risk of autism is that women are more likely to have depleted levels of nutrients

such as folate and iron, as well as higher stress levels, after a recent pregnancy; however, these factors were not tested in the

current study.

 

Study authors suggest the finding is particularly important given trends in birth spacing in the U.S.; between 1995 and 2002,

the proportion of births occurring within 24 months of a previous birth increased from 11 percent to 18 percent. Closely spaced

births occur because of unintended pregnancies but also by choice, particularly among older women who delay childbearing.

 

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