(CNN) – An app designed to track fertility and prevent pregnancy in women 18 and older is the first to win US Food and Drug Administration approval to be marketed as a contraceptive, the agency announced Friday. The Natural Cycles app was approved as part of the agency’s new Digital Health Innovation Action Plan, designed to fast-track approval for new low-to-moderate-risk devices.

“This new app can provide an effective method of contraception if it’s used carefully and correctly,” said Dr. Terri Cornelison, assistant director for the health of women in the FDA’s Center for Devices and Radiological Health, in a statement. “But women should know that no form of contraception works perfectly, so an unplanned pregnancy could still result from correct usage of this device.”

Also Friday, the FDA announced approval of a vaginal ring designed by the global nonprofit research organization the Population Council. Called Annovera, the device is “the first vaginal ring contraceptive that can be used for an entire year,” the FDA said.

According to the Population Council, Annovera is the first in a new class of contraceptives. The soft reusable ring combines a new progestin (segesterone acetate) with a widely used estrogen (ethinyl estradiol) to develop a single product designed to be left in place for 21 days and removed for seven days.

“It is indicated to prevent pregnancy for up to a year and does not require refrigeration, which is particularly important for distribution and use in low-resource settings,” the Population Council said on its website. In partnership with the pharmaceutical company TherapeuticsMD, the council plans to offer the ring at significantly reduced prices to lower-income women at federally designated Title X family planning clinics in the United States.

First contraceptive app

According to the US Centers for Disease Control and Prevention, between 1% and 3% of women use fertility awareness — in which a woman’s body signs such as temperature are measured to predict ovulation — as a form of contraception. However, a study from the University of Iowa found that if more women knew about it, one in five would consider it as an option.

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Natural Cycles hopes to tap into that market. The app uses sperm survival rates, body temperature and menstrual cycles to predict a woman’s fertile days. To use the app, a woman must take her temperature with a basal body thermometer, which provides accurate data to the 10th of a degree, every morning. A red light then warns if there is a risk of pregnancy and to use contraception; a green light says it’s safe to have unprotected sex.

Women who are using birth control or hormonal treatments that inhibit ovulation must stop before using the app, the FDA warned because it could invalidate the app’s assessment. Women with a medical condition with which pregnancy would be associated with a significant risk, such as high blood pressure, diabetes or kidney disease, should not use the app at all. Nor does it provide protection against sexually transmitted infections.

Natural Cycles was developed by nuclear physicist Elina Berglund Scherwitzl, who was part of the Nobel Prize-winning team that discovered the Higgs boson particle, part of a model that explains the fundamental building blocks of the universe. She and her husband developed and marketed the Natural Cycles algorithm after not finding a satisfactory hormone-free contraceptive option on the market.

Launched in Sweden in 2014 as a fertility app to help women who are trying to become pregnant, the app obtained approval last year as a certified contraceptive from the UK’s Medicines and Healthcare products Regulatory Agency.

“This puts the app in the same category as the condom,” the company says on its website.

Fertility awareness

According to the American College of Obstetricians and Gynecologists, the app is a form of contraception called fertility awareness. In the first year of typical use of fertility awareness, between 12 and 24 women of every 100 could become pregnant, the group said. If it is used perfectly — consistently and correctly — that risk falls to one in five pregnancies per 100 women. The CDC lists fertility-awareness methods as among the least effective of all contraceptive options.

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