Our commitment to accuracy begins with high-quality data. All of our calculators are built upon a foundation of peer-reviewed scientific studies and large-scale demographic data. This library contains the primary sources used in the development of our algorithms.
Cycle Timing, Fertility & Conception
Wilcox, A. J., Dunson, D., & Baird, D. D. (2000). The timing of the “fertile window” in the menstrual cycle: day specific estimates from a prospective study. BMJ, 321(7271), 1259–1262.
Link to Source (BMJ)
Faust, L., et al. (2019). Findings from a mobile application-based cohort of 2.7 million menstrual cycles. Scientific Reports, 9.
Link to Source (ScienceDirect)
Martins, M. V., et al. (2022). Effects of trying to conceive using an every-other-day strategy versus fertile window monitoring on stress: a 12-month randomized controlled trial. Human Reproduction, 37(12), 2845–2855.
Link to Source (PubMed)
Age & Fertility
American College of Obstetricians and Gynecologists (ACOG). (n.d.). “Having a Baby After Age 35: How Aging Affects Fertility and Pregnancy”.
Link to Source (ACOG)
Hendershot, G. E., Mosher, W. D., & Pratt, W. F. (1982). Infertility and age: an unresolved issue. Family Planning Perspectives, 14(5), 287–289.
Link to Source (JSTOR)
Martinez, G., Daniels, K., & Chandra, A. (2012). Fertility of men and women aged 15-44 years in the United States: National Survey of Family Growth, 2006-2010. National Health Statistics Reports, (51), 1–28.
Link to Source (CDC)
Contraceptive Effectiveness
Trussell, J. (2011). Contraceptive failure in the United States. Contraception, 83(5), 397–404.
Link to Source (ScienceDirect)
Kost, K., et al. (2008). Estimates of contraceptive failure from the 2002 National Survey of Family Growth. Contraception, 77(1), 10–21.
Link to Source (Guttmacher Institute)
Lifestyle & Demographic Factors
Hassan, M. A., & Killick, S. R. (2004). Negative lifestyle is associated with a significant reduction in fecundity. Fertility and Sterility, 81(2), 384–392.
Link to Source (PubMed)
Twenge, J. M., Sherman, R. A., & Wells, B. E. (2017). Declines in Sexual Frequency among American Adults, 1989-2014. Archives of Sexual Behavior, 46(8), 2389–2401.
Link to Source (Springer)
Lawson, C. C., et al. (2009). Occupational factors and risk of preterm birth in nurses. American Journal of Obstetrics and Gynecology, 200(1), 51.e1–51.e8.
Link to Source (PubMed)