In Reply Dr Tomao and colleagues are concerned that our results may be biased because, for 23% of the study population, information on subfertility diagnosis and number of IVF cycles was obtained from a self-administered questionnaire when medical records were not available. We felt confident using questionnaire data for subfertility diagnosis to limit the amount of missing data because de Boer and colleagues1 reported that in the same study population, the validity of self-reported subfertility causes was satisfactory.
van den Belt-Dusebout AW, van Leeuwen FE, Burger CW. Breast Cancer Risk After Ovarian Stimulation for In Vitro Fertilization—Reply. JAMA. 2016;316(16):1713-1714. doi:10.1001/jama.2016.15243