HealthDay News — Children born from pregnancies with interpregnancy intervals of less than two years or more than six years are at greater risk of autism spectrum disorder (ASD), according to a study published in Pediatrics.

Ousseny Zerbo, PhD, from Kaiser Permanente Northern California (KPNC) in Oakland, and colleagues evaluated medical records data from a cohort of 45,261 children born at KPNC between 2000 and 2009 to determine the association between interpregnancy interval and ASD risk in second-born children.

The researchers found that children born after an interpregnancy interval of <12 months or ≥72 months had a two- to threefold increased risk of ASD compared with children born after an interval of 36 to 47 months. Adjusted hazard ratios (95% confidence intervals) were 3 (1.9-4.7) for an interpregnancy interval of less than six months, 2.1 (1.4-3.3) for an interpregnancy interval of six to eight months, 1.9 (1.3-2.1) for an interpregnancy interval of nine to 11 months, 1.5 (1.1-2.1) for an interpregnancy interval of 12 to 23 months and 2.4 (1.5-3.7) for an interpregnancy interval of at least 72 months. Maternal BMI, change in BMI between pregnancies, parental age, maternal antidepressant medication use, and unfavorable events occurring during the first or second pregnancy did not explain the results.

“The mechanism explaining this association is unknown, and more research is needed,” the authors write.


  1. Zerbo O et al. Pediatrics. 2015; doi:10.1542/peds.2015-1099.