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Time between pregnancies may increase child’s risk for autism

Birth spacing was linked to a child’s increased risk for autism, according to findings recently published in Autism Research.

“To our knowledge, no study has examined associations between interpregnancy interval and autism spectrum disorder and nonASD developmental disabilities in the same study population,” Laura A. Schieve, PhD, National Center on Birth Defects and Developmental Disabilities, CDC, and colleagues wrote. “Thus, it has not been possible to assess whether associations reported between interpregnancy interval and ASD might reflect a more general neurodevelopmental effect.”

Researchers evaluated data from the Study to Explore Early Development (SEED), a CDC initiative to identify factors that put children at risk for ASD. Schieve and colleagues’ cohort contained 524 population controls who were second or later births, 356 ASD cases and 627 developmental disability cases. The ASD cases were further split into groups based on symptom severity, and developmental disability cases were further split if some ASD symptoms were present.

Schieve and colleagues found that among term births, ASD was linked to interpregnancy intervals of less than 18 months (adjusted OR = 1.5; 95% CI, 1.1-2.2) and 60 months or more (aOR = 1.5; 95% CI, 0.99-2.4). Both short (aOR = 2; 95% CI, 1.3-3.3) and long (aOR = 1.8; 95% CI, 0.99–3.2) interpregnancy interval associations were stronger among ASD cases with high severity scores. These associations remained constant after adding several factors potentially related to the causal pathway to regression models.

Researchers also wrote that unadjusted stratified analyses suggested an effect modification between interpregnancy intervals and gestational age (P = .075 with positive links between ASD and both short and long interpregnancy intervals among term births) and analyses of finer gradations of short interpregnancy interval showed the magnitude of effects for links between ASD and interpregnancy intervals of less than 12 months and between 12 and 18 months were similar.

In addition, Schieve and colleagues found that no other developmental disabilities were not linked with either short or long interpregnancy interval — overall, among term births, or in any subgroup examined.

“These findings in concert with those from other studies can inform public health and clinical guidelines about optimal pregnancy spacing,” Schieve and colleagues wrote. “Since pregnancy spacing is potentially modifiable, it is particularly important to more fully understand the underlying explanation for the ASD–interpregnancy interval associations such that women can be fully informed of the potential risks associated with short and long interpregnancy intervals.” – by Janel Miller

References: CDC. Study to Explore Early Development (SEED). Available at: https://www.cdc.gov/ncbddd/autism/seed.html. Accessed Nov. 22, 2017.

Disclosures: The authors report no relevant financial disclosures.