The association between the interpregnancy interval and autism spectrum disorder in a Canadian cohort

Abstract

OBJECTIVES: Two studies reported an increased risk of autistic disorder in children conceived less than 12 months after a previous birth. Our objective was to examine the association between the interpregnancy interval (IPI) and autism spectrum disorder (ASD) in a Canadian cohort.METHODS: Using administrative datasets housed at the Manitoba Centre for Health Policy, we identified pairs of first-and second-born singleton siblings born between 1988 and 2005. Diagnoses of ASD were ascertained by searching physician billing claims, hospital discharge abstracts, education data, and a database containing information on individuals identified for a 2002-2007 ASD surveillance program in Manitoba. Logistic regression models were fit to examine the association between the IPI and ASD in 41,050 second-born siblings where the first-borns did not have ASD, using IPIs of ≥36 months as the reference category and specifying three case groups. Case Group 1 included individuals with at least one ASD code (n = 490); Case Group 2 included those with two or more ASD codes (n = 375); and Case Group 3 comprised individuals with a record in the ASD surveillance program database (n = 141). RESULTS:The adjusted odds ratios (ORs) for IPIs shorter than 12 months ranged from 1.22 (95% CI: 0.91-1.63) for Case Group 1 to 1.72 (95% CI: 0.96-3.06) for Case Group 3. When the case groups were restricted to individuals with more severe ASD, the ORs increased and were significant for Case Groups 1 and 2.CONCLUSION: Our findings also support an association between short IPIs and more severe ASD.KEY WORDS: Autism; interpregnancy interval; secondary analysis; administrative data; record linkage; Manitoba Centre for Health Policy La traduction du résumé se trouve à la fin de l'article.

Birth Spacing and Risk of Autism and Other Neurodevelopmental Disabilities: A Systematic Review

“…The remaining study reported a nonsignificant greater risk of ASD among children born after an IPI of <12 months (adjusted OR 1.72, 95% CI 0.96-3.06). 32 However, a sensitivity analysis restricted to individuals with more severe ASD revealed a significant association between IPIs of <12 months and this disorder. Three studies also found a significant association between ASD and long IPIs (≥60 months, 31 ≥72 months, 34 and ≥84 months 33 ).…”

“…A total of 12 studies (6 cohort, 5 cross-sectional, and 1 case-control), including 1 334 569 children, met the inclusion criteria. [28][29][30][31][32][33][34][35][36][37][38][39] The individual characteristics and main findings of the studies included in the systematic review are shown in Table 1. Seven studies provided data on ASD, 28 …”

“…[28][29][30][31][32][33][34] Three studies showed a U-shaped association between IPI and the risk of ASD. 31,33,34 Six studies found a significant association between short IPIs (<12 months, 30,31,33 <18 months, 29 <24 months, 34 and <36 months 28 ) and increased risk of ASD.…”

Understanding environmental contributions to autism: Causal concepts and the state of science

“…As recently systematically reviewed, a short IPI has been consistently associated with ASD, conferring about 2‐fold higher risk for children born after an IPI less than 12 months compared with those born after 36 or more months [Cheslack‐Postava, Liu, & Bearman, ; Cheslack‐Postava et al, ; Conde‐Agudelo, Rosas‐Bermudez, & Norton, ; Coo et al, ; Durkin, DuBois, & Maenner, ; Gunnes et al, ; Zerbo, Yoshida, Gunderson, Dorward, & Croen, ]. Short IPI may indicate maternal depletion of nutrients, such as folate, as essential nutrients are preferentially distributed to the developing fetus during pregnancy, and can remain low for up to a year postpartum [O'Rourke, Redlinger, & Waller, ; Smits & Essed ; van Eijsden, Smits, van der Wal, & Bonsel, ].…”

“…Some evidence for dose-response, however three studies also showed higher risk with longer intervals. Associations could result from maternal nutrient depletion or cultural, family planning, or lifestyle factors.Cheslak-Postava et al[2011];Dodds et al [2011];Gunnes et al [2013];Cheslack- Postava et al [2014];Coo et al [2015];Durkin et al [2015];Zerbo et al [2015]; Conde-Agudelo et al[2016]…”