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Birth Spacing and Risk of Autism and Other Neurodevelopmental Disabilities: A Systematic Review
Agustín Conde-Agudelo1, Anyeli Rosas-Bermudez2, Maureen H Norton3
1World Health Organization Collaborating Centre in Human Reproduction, Universidad del Valle, Cali, Colombia; and condeagu@hotmail.com.
Insights
Short interpregnancy intervals (IPIs) increase autism spectrum disorder (ASD) risk. Long IPIs may also elevate ASD risk. This systematic review highlights birth spacing as a factor in neurodevelopmental outcomes.
Area of Science:
- Neuroscience
- Developmental Pediatrics
- Epidemiology
Background:
- Interpregnancy intervals (IPIs) are the time between live births.
- Both short and long IPIs have been anecdotally linked to increased autism spectrum disorder (ASD) risk.
- Systematic evaluation of this association is lacking.
Purpose of the Study:
- To systematically evaluate the relationship between interpregnancy intervals (IPIs) and the risk of autism spectrum disorder (ASD).
- To examine the association between birth spacing and other neurodevelopmental disabilities.
Main Methods:
- Systematic review of observational studies published up to December 2015.
- Data extraction by two independent reviewers on study characteristics, IPIs, and outcomes.
- Pooled analysis of adjusted odds ratios (ORs) for ASD and other neurodevelopmental disabilities.
Main Results:
- Seven studies (1,140,210 children) found short IPIs (<12 months) significantly increased ASD risk (pooled adjusted OR 1.90).
- The association was stronger for autistic disorder (pooled adjusted OR 2.62).
- Three studies indicated long IPIs (≥36 months) also increased ASD risk. Short intervals were linked to developmental delay and cerebral palsy.
Conclusions:
- Short interpregnancy intervals (IPIs) are associated with a significantly increased risk of autism spectrum disorder (ASD).
- Long interpregnancy intervals (IPIs) also appear to increase the risk of ASD.
- Birth spacing is a potential factor influencing neurodevelopmental outcomes.
Context:
Both short and long interpregnancy intervals (IPIs) have recently been associated with increased risk of autism spectrum disorder (ASD). However, this association has not been systematically evaluated.
Objective:
To examine the relationship between birth spacing and the risk of ASD and other neurodevelopmental disabilities.
Data Sources:
Electronic databases from their inception to December 2015, bibliographies, and conference proceedings.
Study Selection:
Observational studies with results adjusted for potential confounding factors that reported on the association between IPIs or birth intervals and neurodevelopmental disabilities.
Data Extraction:
Two reviewers independently extracted data on study characteristics, IPIs/birth intervals, and outcome measures.
Results:
Seven studies (1 140 210 children) reported an association between short IPIs and increased risk of ASD, mainly the former subtype autistic disorder. Compared with children born to women with IPIs of ≥36 months, children born to women with IPIs of <12 months had a significantly increased risk of any ASD (pooled adjusted odds ratio [OR] 1.90, 95% confidence interval [CI] 1.16-3.09). This association was stronger for autistic disorder (pooled adjusted OR 2.62, 95% CI 1.53-4.50). Three of these studies also reported a significant association between long IPIs and increased risk of ASD. Short intervals were associated with a significantly increased risk of developmental delay (3 studies; 174 940 children) and cerebral palsy (2 studies; 19 419 children).
Limitations:
Substantial heterogeneity, and few studies assessing neurodevelopmental disabilities other than ASD.
Conclusions:
Short IPIs are associated with a significantly increased risk of ASD. Long IPIs also appear to increase the risk of ASD.
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