Contraceptive effectiveness of a digital contraceptive with a wearable device vs an oral thermometer

Purpose To inform contraceptive decisions, we aimed to compare the pregnancy and continuation rates of a digital contraceptive, when paired with temperature data from wearable devices versus from oral thermometers.Materials and methods We employed prospectively collected data from women who registered to Natural Cycles for contraception between the 1st of August 2022 and the 1st of September 2024. Using Kaplan-Meier curves, we calculated 13-cycle pregnancy rates in typical and perfect use as well as one-year continuation rates. We estimated the association of known demographic characteristics with pregnancy rates using a multivariate Cox proportional hazards model.Results Among the 195 027 presumed fertile women whom we analysed, the unadjusted 13-cycle pregnancy rate for wearable device users was significantly lower than for oral thermometer users both in typical use (4.7% vs 7.3%; p < 0.001) and in perfect use (2.0% vs 2.9%; p < 0.001). However, when adjusting for demographics, measuring with a wearable device rather than a thermometer was not independently associated with pregnancy. We observed one-year continuation rates of 75.8% for wearable device users and 56.4% for thermometer users.Conclusions Findings from this study suggest that combining a contraceptive app with a wearable device rather than an oral thermometer does not affect pregnancy rates when adjusting for socio-demographic variables. However, the substantial increase in continuation implies greater user convenience.