Natural Cycles, as well as the rhythm method, uses your body’s natural signs in order to identify your fertile days. However, Natural Cycles differs in many ways – including how it works, how one should use it, and how effective it is.
The rhythm method (also known as the calendar method), fertility awareness method (FAM/FABM), or natural family planning (NFP), works by tracking menstrual history to predict when you will ovulate. Those that use any of the aforementioned methods are responsible for all of the calculations and interpretations themselves, usually done by charting on paper.
Natural Cycles uses a smart algorithm that performs the analysis of your data and gives you either a green day, when no protection is needed, or a red day, when you should use a barrier method (such as a condom) or abstain from sex in order to effectively prevent a pregnancy. The Natural Cycles’ algorithm has been intricately designed to account for sperm survival, variation in cycle length, ovulation day, temperature fluctuations, and the length of the follicular and luteal phase. Cervical fluids (and other indicators as cervix position) are a fertility indicator but we have chosen not to include them because learning how to interpret takes both time and practice. Natural Cycles is designed to be as user-friendly as possible, allowing new Cyclers to get started right away.
Natural Cycles’ effectiveness rate of 93% with typical use is based on scientific studies and annual audits. This means that Natural Cycles is the first app that has been assessed and deemed effective enough in preventing pregnancy to be categorized as a method of birth control in Europe and the US (1). Traditional Fertility Awareness-Based Methods (FABM) are associated with an effectiveness rate of 76% with typical use (2). It is, however, important to keep in mind that no method of birth control is 100% effective.
(1) Berglund Scherwitzl E, et al. Contraception. 2017;96(6):420–425.
(2)Trussell J. Contraceptive failure in the United States. Contraception 2011;83:397–404.