Summary

Advice

The technology described in this briefing is the Natural Cycles app for monitoring fertility to prevent a pregnancy for people wishing to use a calendar fertility-awareness method of contraception. Other more reliable forms of contraception are available.
The innovative aspects are that Natural Cycles is the first fertility-awareness app that comes with a basal thermometer and has been CE-marked as a medical device.
The intended place in therapy is as a fertility-awareness contraception method. It would be used as a strategy to monitor ovulation, predict fertility, and may be used alongside abstinence or a barrier contraceptive method.
The main points from the evidence summarised in this briefing are from 3 studies (2 retrospective analyses and 1 prospective observational study). These included 70,113 people using the app at home with typical follow-up of 6 to 9 months. They show that Natural Cycles can be used as a fertility-awareness contraception method. No evidence was identified on using the app to help plan a pregnancy.
Key uncertainties around the evidence or technology are that Natural Cycles has not been directly compared with any other contraception.
The cost of Natural Cycles is £49.99 for a 1‑year subscription. Most other contraception is available at no charge to the user from standard NHS services.