I think jaidoretta's comment is a bit too optimistic about fertility-awareness methods. The CDC has an information sheet about the effectiveness of different m

I think jaidoretta's comment is a bit too optimistic about fertility-awareness methods. The CDC has an information sheet about the effectiveness of different methods of contraception[1] which cite on the order of 18 pregnancies a year for these methods. Interestingly, newer fertility-awareness methods appear to be more effective than this estimate[2]. [1] http://www.cdc.gov/reproductivehealth/UnintendedPregnancy/PDF/Contraceptive_methods_508.pdf http://www.cdc.gov/reproductivehealth/UnintendedPregnancy/PD... [2] http://www.sciencedirect.com/science/article/pii/S0015028204012518 http://www.sciencedirect.com/science/article/pii/S0015028204...