A mobile fertility app could become the first to be prescribed on the NHS alongside condoms and the pill after being officially approved for use as contraception.

Developed by two Swedish physicists, Natural Cycles monitors female fertility through daily temperature, and uses an algorithm to plot this on an in-app calendar.

Boasting over 150,000 users in 161 countries who pay £6.99 per month, the app was part of a clinical study in 2016 of one million women.

German testing organisation Tüv Süd, a certification body employed by the Department of Health to test the safety of new drugs and medical devices, claimed it could be as effective as the contraceptive pill.

Dr Elina Berglund, CTO and co-founder of Natural Cycles, said: “Women around the world are interested in exploring effective non-hormonal, non-invasive forms of contraception - and now they have a new, clinically verified and regulatory approved option to choose from.

"Our high quality clinical studies, together with the required regulatory approvals, means we can provide women everywhere with a new option for contraception."

Natural Cycles

She added: “Natural Cycles is a great example of how technology is helping women to conceive in an easy and accessible way."

“We know we’re dealing with women’s lives here and we take that very seriously.

”The app can also be used for infertile couples to identify the cause of infertility.”

According to research published in the European Journal of Contraception and Reproductive Health Care, Natural Cycles scored similar results to the pill on what is known as the Pearl Index.

This measures the effectiveness of birth control methods by measuring how many subjects out of 100 will experience an accidental pregnancy within the first year of use.

On this index, the pill has a score of 0.3, which means three in every 1,000 women using the contraception ‘perfectly’ will become pregnant.

Natural Cycles was given a Pearl Index score of 0.5.

After ovulation, increased levels of progesterone make women’s bodies up to 0.45°C warmer.

Users input their daily temperature into the app, which compares their readings against those in its dataset.

If the app determines it’s safe to have unprotected sex it will show a green day in its calendar - days when it’s not safe to have unprotected sex are shown as red.

Natural Cycles was launched in 2014 and raised $6m funding in 2016 to conduct new clinical studies and aid international expansion.