The Standard Days Method® is a fertility awareness-based method of family planning in which users avoid unprotected intercourse during cycle day 8 through 19. The method is most appropriate for women with cycles that usually range 26-32 days. The clinical trial tested the contraceptive efficacy of the Standard Days Method. A total of 478 women, age 18-39 years, in Bolivia, Peru, and the Philippines, with self-reported cycles of 26-32 days, desiring to delay pregnancy at least one year were admitted to the study and followed for up to 13 cycles of method use.