Meeting paper
SMFM paper
Autism risk in small- and large-for-gestational-age infants

Presented at the 32nd annual meeting of the Society for Maternal-Fetal Medicine, Dallas, TX, Feb. 6-11, 2012.
https://doi.org/10.1016/j.ajog.2012.01.044Get rights and content

Objective

We sought to determine whether small-for-gestational age (SGA) and large-for-gestational age (LGA) birthweights increase autism risk.

Study Design

This was a retrospective cohort analysis comparing children with autism (n = 20,206) within a birth cohort (n = 5,979,605). Stratification by sex and birthweight percentile (SGA, <5th or 5-10th percentile; appropriate size for gestational age [GA], >10th to <90th percentile; LGA, either 90-95th or >95th percentile) preceded Cochran-Mantel-Haenszel analysis for GA effect, and multivariate analysis.

Results

Autism risk was increased in preterm SGA (<5th percentile) infants 23-31 weeks (adjusted odds ratio [aOR], 1.60; 95% confidence interval [CI], 1.09–2.35) and 32-33 weeks (aOR, 1.83; 95% CI, 1.16–2.87), and term LGA (>95th percentile) infants 39-41 weeks (aOR, 1.16; 95% CI, 1.08–1.26), but was decreased in preterm LGA infants 23-31 weeks (aOR, 0.45; 95% CI, 0.21–0.95).

Conclusion

SGA was associated with autism in preterm infants, while LGA demonstrated dichotomous risk by GA, with increased risk at term, and decreased risk in the premature infants. These findings likely reflect disparate pathophysiologies, and should influence prenatal counseling, pediatric autism screening, and further autism research.

Section snippets

Materials and Methods

This was a population-based cohort study, approved by the California Protection of Human Subjects Committee; the Office of Statewide Health Planning and Development (OSHPD); and the University of California, Davis Human Subjects Committee.

We utilized a database constructed by our group in 2007 to evaluate perinatal risk factors for developmental disabilities. An 11-year birth cohort (Jan. 1, 1991, through Dec. 31, 2001) was identified within a database provided by the California OSHPD, which

Results

Within the cohort of 5,979,605 children born in California from 1991 through 2001, 21,717 children with autism were identified. The remainder of the birth cohort served as the control group (n = 5,957,888). Male sex, advanced maternal and paternal ages, Asian race, chronic hypertension, preeclampsia, any form of diabetes, high birth order (≥3), short interpregnancy interval, and twin gestations were significantly associated with autism (Table 2).

Within the entire population, autism risk was

Comment

Our large birth-cohort analysis describes autism risk by BW percentile, stratified by GA at birth. Within the entire cohort, both SGA and LGA BW were associated with autism. Stratification by GA revealed that only preterm SGA infants (<34 weeks) and term LGA infants (39-41 weeks) had a significantly increased risk for autism, while preterm LGA infants (<32 weeks) were protected against autism.

The strengths of this analysis lie primarily in the large number of children with autism diagnosed

Conclusion

Autism risk is significantly increased at both extremes of BW appropriateness. Stratification by GA yielded a more complex relationship, with increased risk seen only in preterm SGA infants and term LGA infants. Unexpectedly, LGA BW correlated with a significantly lower autism risk in children born <32 weeks. The nature of the associations between SGA and LGA BW and autism risk remains uncertain. We hope to further investigate perinatal conditions surrounding term delivery of LGA infants, and

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    Supported in part by National Institutes of Health grant number R03-HD050575.

    The authors report no conflict of interest.

    The racing flag logo above indicates that this article was rushed to press for the benefit of the scientific community.

    Reprints not available from the authors.

    Cite this article as: Moore GS, Kneitel AW, Walker CK, et al. Autism risk in small- and large-for-gestational-age infants. Am J Obstet Gynecol 2012;206:314.e1-9.

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