Thimerosal in Pregnancy Not Tied to Autism


Exposure to thimerosal-containing Rh immunoglobulin during pregnancy is not associated with an increased risk of having a child with an autism spectrum disorder, said Dr. Judith H. Miles and T. Nicole Takahashi.

Overall, 214 mothers of 230 children receiving treatment for an autism spectrum disorder at the autism clinic at the University of Missouri-Columbia were not more likely to be Rh-negative than were 65 mothers of children receiving other medical genetic treatment there (15.4% vs. 15.4%), said Dr. Miles and Ms. Takahashi of the university (Am. J. Med. Genet. A 2007;doi:10.1002/ajmg.a.31846).

The proportion of Rh-negative women was similar among other controls, including 15.2% among all patients at the university hospital whose blood was typed between April 1, 2005, and March 31, 2006, and 17.7% among blood donors at the Missouri Illinois Regional Red Cross in calendar year 2005, they reported.

Mothers of children with an autism spectrum disorder were also not more likely than the control patients receiving other medical genetic treatment to have been exposed to antepartum thimerosal-containing Rh immunoglobulin (13.9% vs. 14.8% of those pregnant prior to 2002) or to have an Rh-incompatible pregnancy (61% vs. 50%).

These findings provide further evidence that exposure to ethylmercury in thimerosal does not explain the increased prevalence of autism in recent years, the authors said. “We hope this report … will offset some of the decreased compliance with immunization recommendations which is known to increase morbidity and mortality from childhood infectious diseases.” They also noted the importance of these findings for the international use of thimerosal-containing vaccines, which are more affordable because they allow the preservation of multidose vials.

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