FDA’s de novo premarket review pathway for low-to-moderate-risk devices. In its announcement, the agency noted that it will be establishing “special control” criteria to make clear its accuracy, reliability, and pregnancy prevention effectiveness expectations for this and future contraception apps.

Data supporting the decision included clinical studies of 15,570 users who used the app for an average of eight months. In these, the Natural Cycles demonstrated a “perfect use” failure rate of 1.8 percent, implying that 18 women in 1,000 using app correctly for a year will become pregnant, and a “typical use” failure rate of of 6.5 percent for those occasionally using the app incorrectly.