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May 4, 1979

Possible Teratogenic Hyperthermia and Marathon Running

Author Affiliations

University of Oklahoma Health Sciences Center Oklahoma City

JAMA. 1979;241(18):1892. doi:10.1001/jama.1979.03290440016013

To the Editor.—  The article by John D. Cantwell, MD (240:1409, 1978), extolled the many benefits of running. I would like to add a note of caution for women runners; namely, that marathon running may pose a teratogenic risk during early pregnancy. This warning seems warranted on the basis of the following evidence: First, marathon runners experience sustained increases of core temperature into the "high fever" range.1,2 Second, recent studies3-5 have shown an association between birth defects and episodes of maternal hyperthermia.Because the first half of gestation is apparently the period of greatest risk for hyperthermia-induced birth defects,4 a substantial number of women may already have trained for and run the marathon during this critical period, either because they were unaware of or unhindered by their pregnancy. A study of the outcomes of such pregnancies might be informative in regard to the relationship between high maternal