A quarterly publication of the Autism Research Institute

The Autism Research Review International is quarterly publication of the Autism Research Institute

Spring, 2016 | Number 2, Volume 30

Close pregnancy spacing may up risk of ASD in children

A new research review adds to evidence that closely spaced pregnancies are a risk factor for autism spectrum disorders (ASD). 

Agustín Conde-Agudelo and colleagues examined data from seven studies containing data on more than one million children. The researchers found that compared with children born to women with interpregnancy intervals of 36 months or longer, children born to women with intervals under 12 months had nearly twice the risk of receiving any ASD diagnosis and had more than double the risk for developing “classical” autism. The researchers speculate that women who have closely spaced pregnancies may have depleted levels of folic acid, which is necessary for proper brain development. 

Three of the studies also found an association between interpregnancy intervals greater than five years and a greater risk for ASD—particularly Asperger’s syndrome and pervasive developmental disorder. The researchers say that low fertility, unintended pregnancy, or maternal inflammation may play a role in this phenomenon. 

“Based on the current best available evidence,” Conde-Agudelo says, “it appears that the ideal interpregnancy interval—the time elapsed between the birth of the immediate older sibling and the conception of the younger sibling—is two to five years, in order to reduce the risk of autism.”


“Birth spacing and risk of autism and other neurodevelopmental disabilities: A systematic review,” Agustín Conde-Agudelo, Anyeli RosasBermudez, and Maureen H. Norton, Pediatrics, May 2016. Address: Agustín Conde-Agudelo, World Health Organization Collaborating Center in Human Reproduction, University of Valle, Cali, Colombia. 


“Short gap between pregnancies tied to higher autism risk?,” HealthDay, April 7, 2016.