Fertile-window misclassification in period-tracking applications and associated pregnancy risk: a large observational analysis.

Abstract

Given the widespread contraceptive use of period-tracking applications, we aimed to quantify misclassification of biologically fertile days and associated pregnancy risk by calendar-based and BBT-supported period-tracking applications and compare it with an FDA-cleared and CE-marked digital contraceptive. We conducted an observational analysis of 543,167 cycles from users of a fertility application. Biologically fertile days were identified using urinary luteinizing hormone tests. Outcomes inclu