To the Editor.—
We have reviewed the article by Jick et al. As with another reviewer,1 we have found a disturbing number of flaws in the methodology.The authors designate as a spermicide "user" any woman who filled a prescription for a spermicide within 600 days of delivery or abortion. This interval is extremely arbitrary; 600 days before abortion is not the same as 600 days before parturition. If any attempt is to be made to compare the results of pregnancies with the results of abortions or to use the results to support a hypothesis on common mechanisms, then an interval based on the time of conception should be chosen. Moreover, no evidence is provided that "users" have been classified correctly. How many of the "nonusers" have used vaginal spermicides in the past (no prescription is required to purchase these products) and how many of the "users" used their
Felarca LC, Wardell DM, Rowles B. Vaginal Spermicides and Congenital Disorders. JAMA. 1981;246(23):2677. doi:10.1001/jama.1981.03320230011004
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