A groundbreaking new app could be set to replace the contraceptive pill in preventing unwanted pregnancies.
Based on a unique algorithm that predicts a woman's daily fertility throughout her monthly cycle, the Natural Cycle app offers a hormone-free alternative to contraceptive methods such as the pill, the injection and the implant.
A new study of 4,000 women found the app to have a similar efficacy to the pill, but without any of the hormonal side effects.
The study, which involved Swedish women aged between 20 - 35 and was recently published in the European Journal of Contraception and Reproductive Health Care, found Natural Cycles had a similar Pearl Index score to the pill.
The Pearl Index works by calculating how many women out of every 100 will accidentally get pregnant within the first year of using a contraceptive method.
While the pill has a Pearl Index score of 0.3, meaning three in every 1,000 women who use it will get pregnant, Natural Cycles was found to have a score of 0.5, meaning five in every 1,000 women who use it will get pregnant.
So how does it work?
Most women are fertile for a maximum of six days per cycle, with the fertility window opening around five days before ovulation and closing on the day of ovulation.
The app measures fertility by monitoring body temperature, which works as an indirect measure of the hormone levels in a woman's body. Users are required to measure their temperature every morning and input their score into the app, which can then calculate the days on which they are most fertile and therefore most likely to get pregnant. Once the temperature is inputted each day, the user will see either a green "not fertile" screen or a red "fertile" screen.
While there are already a number of apps on the market that claim to measure fertility, Natural Cycle's daily measurement of body temperature makes it uniquely reliable. The app's website claims it is "clinically tested and tailored for you" and promises to measure fertility and ovulation as well as providing a period tracker. By monitoring a user's temperature, it is also suitable for women who have irregular monthly cycles, as it does not focus on the traditional idea of a 28 day cycle.
The app can also map the progress of a pregnancy through a user's temperature, meaning it is can also work for pregnant women looking for an easy way to monitor their baby's development. It can also detect when a woman has had a miscarriage.
One of the creators of the app, Dr Elina Berglund, hopes Natural Cycles will help shift the focus of contraception away from hormones.
She told The Metro, "Natural Cycles uses data instead of chemicals to prevent pregnancies, thereby allowing women to educate and empower themselves and take control of their fertility. The future of birth control lies in knowing your body rather than altering it with hormonal contraceptives, and we are excited to be leading the way and creating a future where every pregnancy is wanted."
And Professor Kristina Gemzell, one of the authors of the study and a senior physician at the Swedish medical university Karolinska Institutet, added: "More and more women, especially in the age group of 20-30, tend to abstain from hormonal contraception and desire a hormone-free alternative.
"It is important to increase choice among contraceptives for women and inform them about their pros and cons."
Natural Cycles is free to download now from the App Store, with a monthly fee of £6.99 or a yearly subscription of £49.99.