Source:  Data from Rothman, K. J. 1982 Spermicide use and Down's syndrome. American Journal of Public Health 72: 399-401. https://doi.org/10.2105/ajph.72.4.399. Reprinted in Rothman, K. J., S. Greenland, and T. L. Lash. 2008. Modern Epidemiology. 3rd ed. Philadelphia: Lippincott Williams & Wilkins.