*1. Hassan, M. A. M. & Killick, S. R. Negative lifestyle is associated with a significant reduction in fecundity. Fertil. Steril. 81, 384–392 (2004). *2. Practice Committee of American Society for Reproductive Medicine in collaboration with Society for Reproductive Endocrinology and Infertility. Optimizing natural fertility: a committee opinion. Fertil. Steril. 100, 631–637 (2013). *3. Bunting, L. & Boivin, J. Knowledge about infertility risk factors, fertility myths and illusory benefits of healthy habits in young people. Hum. Reprod. 23, 1858–1864 (2008). *4. Practice Committee of the American Society for Reproductive Medicine. Smoking and infertility. Fertil. Steril. 86, S172–7 (2006). *5. Said, T. M., Ranga, G. & Agarwal, A. Relationship between semen quality and tobacco chewing in men undergoing infertility evaluation. Fertil. Steril. 84, 649–653 (2005). *6. Augood, C., Duckitt, K. & Templeton, A. A. Smoking and female infertility: a systematic review and meta-analysis. Hum. Reprod. 13, 1532–1539 (1998). *7. Cao, S. et al. Smoking and risk of erectile dysfunction: systematic review of observational studies with meta-analysis. PLoS ONE 8, e60443 (2013). *8. Braga, D. P. de A. F. et al. Food intake and social habits in male patients and its relationship to intracytoplasmic sperm injection outcomes. Fertil. Steril. 97, 53–59 (2012). *9. Sanger, W. G. & Friman, P. C. Fit of underwear and male spermatogenesis: a pilot investigation. Reprod. Toxicol. 4, 229–232 (1990). *10. Jung, A., Leonhardt, F., Schill, W.-B. & Schuppe, H.-C. Influence of the type of undertrousers and physical activity on scrotal temperature. Hum. Reprod. 20, 1022–1027 (2005). *11. Tielemans, E. et al. Occupationally related exposures and reduced semen quality: a case-control study. Fertil. Steril. 71, 690–696 (1999). *12. Garolla, A. et al. Seminal and molecular evidence that sauna exposure affects human spermatogenesis. Hum. Reprod. 28, 877–885 (2013). *13. Sheynkin, Y., Jung, M., Yoo, P., Schulsinger, D. & Komaroff, E. Increase in scrotal temperature in laptop computer users. Hum. Reprod. 20, 452–455 (2005). *14. Schrader, S. M., Breitenstein, M. J. & Lowe, B. D. Cutting off the nose to save the penis. J Sex Med 5, 1932–1940 (2008). *15. Huang, V., Munarriz, R. & Goldstein, I. Bicycle riding and erectile dysfunction: an increase in interest (and concern). J Sex Med 2, 596–604 (2005). *16. Goldstein, I., Lurie, A. L. & Lubisich, J. P. Bicycle riding, perineal trauma, and erectile dysfunction: data and solutions. Curr Urol Rep 8, 491–497 (2007). *17. Levitas, E. et al. Relationship between the duration of sexual abstinence and semen quality: analysis of 9,489 semen samples. Fertil. Steril. 83, 1680–1686 (2005). *18. Chiba, K., Yamaguchi, K., Li, F., Ando, M. & Fujisawa, M. Finasteride-associated male infertility. Fertil. Steril. 95, 1786.e9–11 (2011). *19. Tu, H. Y. V. & Zini, A. Finasteride-induced secondary infertility associated with sperm DNA damage. Fertil. Steril. 95, 2125.e13–14 (2011). *20. Rothman, K. J. et al. Volitional determinants and age-related decline in fecundability: a general population prospective cohort study in Denmark. Fertil. Steril. 99, 1958–1964 (2013). *21. Glaser, R. L. & Jabs, E. W. Dear old dad. Sci Aging Knowledge Environ 2004, re1 (2004). *22. Stewart, A. F. & Kim, E. D. Fertility concerns for the aging male. Urology 78, 496–499 (2011). *23. Kovac, J. R. et al. The effects of advanced paternal age on fertility. Asian J. Androl. 15, 723–728 (2013). *24. Toriello, H. V.& Meck, J. M., for Professional Practice and Guidelines Committee. Statement on guidance for genetic counseling in advanced paternal age. Genet. Med. 10, 457–460 (2008).