Time Between Pregnancies May Influence Autism Risk

the MPR take:

Research indicates that both short and long interpregnancy intervals (IPI) may increase the risk of adverse conditions for fetal development, with a short IPI associated with a greater risk of folate depletion or unresolved inflammation from the preceding pregnancy and a longer IPI with a greater risk of preeclampsia. Three previous studies linked shorter IPI with a higher relative risk for autism spectrum disorders (ASD) in limited populations, but is this applicable across a variety of different populations? Published in the Journal of the American Academy of Child & Adolescent Psychiatry, an analysis of 2,208 non-firstborn children in Finland born from 1987-2005 and diagnosed with ASD sought to assess IPI and autism risk compared to 5,163 matched controls. The greatest risk of ASD was found among children with IPI <12 months (OR= 1.50, 95% CI=1.28, 1.74), but also ≥120 months (95% CI=1.12, 1.85). When further evaluated based on ASD subtypes, IPI of <24 months was associated with a greater risk of childhood autism and pervasive developmental disorder-not otherwise specified than Asperger syndrome. The authors state that although the mechanisms for both associations may differ, unintended pregnancy may be the common factor; women with an unintended pregnancy are more likely to smoke, use alcohol, medications, or illicit drugs, delay prenatal care, and are less likely to take folic acid or prenatal vitamins. Inflammation is another possible link, as short IPI may result in unresolved inflammation from the previous pregnancy and longer IPI could lead to increased inflammation due to its impact on BMI (increased BMI associated with higher C-reactive protein levels). 

Both short and long interpregnancy intervals (IPI) are believed to present possible adverse conditions for fetal development. Short IPI has recently been associated with increased risk of autism, but whether long IPI increases risk for autism spectrum disorders (ASD) has not been thoroughly investigated. We investigated the association between short and long IPI in a Finnish population–based study.