The technology

Natural Cycles (Natural Cycles Nordic AB) is an app available for iOS and Android mobile devices. The user inputs daily basal body temperature measurements and menstruation data. A proprietary algorithm then uses this information to predict ovulation and fertility. The app will be able to provide a more accurate prediction for the user as they input more data. The user can choose to share their anonymised data with the company (for research purposes).

The results for each day are reported as either a 'green day', which means the user is unlikely to be fertile; or a 'red day', which means the user is likely to be fertile. This means they should either abstain from sex or use barrier contraceptives to avoid pregnancy. It is also possible to switch modes in the app, so the data can be used to tell the user when they are most likely to be able to conceive, if they are trying to get pregnant.

The app is unlikely to be suitable for people with highly irregular menstrual cycles. This is because predicting fertility is more difficult in these circumstances, resulting in an increased number of 'red days' (when the user must abstain from sex or use barrier contraceptives). The user must also take their basal temperature each morning as soon as they wake up, so a regular sleeping pattern improves the accuracy of this.


Natural Cycles is the first app-based contraceptive with a CE mark that integrates basal thermometer body temperature readings. Natural Cycles differs from other non-hormonal contraception methods (such as fertility awareness planning on a calendar) because it is easier to use and training is not needed.

Current care pathway

There is a wide range of contraception methods available to people in the UK. These include barrier methods (condoms, caps and diaphragms), hormonal methods (combined pill, progesterone-only pill, contraceptive injections and patches), and other devices (implants, intrauterine devices and systems, and vaginal rings). Natural family planning (fertility awareness) can also be used as a method of contraception, but the effectiveness of this method depends on appropriate education and adherence. Only barrier contraceptives can protect against sexually transmitted diseases.

NICE's guideline on long-acting reversible contraception has been identified as relevant to this care pathway.

Population, setting and intended user

Natural Cycles may be used alongside barrier contraceptives or instead of other fertility-awareness methods. It works best with a regular menstrual cycle and sleeping pattern.

Natural Cycles is most likely to be used by people who prefer to use a non-hormonal method, and when other methods of contraception are unsuitable or contraindicated.

The app will be used at home and includes instructions on its correct use. It is expected that minimal input from clinicians will be needed.


Technology costs

Natural Cycles costs £49.99 for a 1-year subscription. This includes the basal thermometer.

Costs of standard care

Most types of contraception are available free of charge as part of standard NHS services. Some people may choose to pay for some methods because of convenience of access or for other reasons. The cost of the oral contraceptive pill is between £11 and £18 per year to the NHS.

Resource consequences

Natural Cycles does not need a prescription or consultation. The company states that it is currently being used by about 250,000 people in the UK.

If more people use the Natural Cycles app as a method of contraception there may be a decrease in the number of appointments for contraception advice. However, if Natural Cycles is not as effective at preventing pregnancy as the methods users used before Natural Cycles, there may be an increase in resources needed for a termination of pregnancy or delivery of an unplanned pregnancy.