Contraceptive App Natural Cycles Blamed for Playing Role in 37 Unwanted Pregnancies

An app that promises to offer “an effective method of natural contraception” has been accused of causing nearly 40 unwanted pregnancies.

Natural Cycles, which analyzes a woman’s individual menstrual cycle to inform her when she’s “fertile” and not, caused 37 women to become pregnant, ultimately forcing them to visit hospitals for abortions, Swedish publication SVT is reporting. The claims, which were earlier reported on by The Verge, were made to the Swedish regulator Medical Product Agency (MPA).

The Natural Cycles company was founded by a couple who wanted a safer way form of contraception that doesn’t rely on hormones. The app requires women to take their temperature each day and input the reading into the app. On the assumption that women can only become pregnant on “up to six days in one cycle,” among others, the app gives a reading to tell them whether they’re fertile that day or not. Natural Cycles says on its site that women may “have sex without protection” on the days they’re described as “not fertile.”

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“Natural Cycles is backed by a unique algorithm that takes your temperature and many other factors like sperm survival, temperature fluctuations and cycle irregularities into account,” the company says on its site. “It not only detects ovulation, fertility and the different stages of your cycle, it also calculates accurate predictions for upcoming cycles.”

The European Union in August made Natural Cycles the first app certified as a form of contraception. On its website, Natural Cycles said a study found a “perfect use failure rate” 1%. When women don’t use it exactly as prescribed, the failure rate jumps to 7%.

It’s unclear from the Swedish report whether Natural Cycles is indeed to blame for the unwanted pregnancies. However, in a statement to Fortune, a company spokesman said that it’s launching an internal investigation into the matter and acknowledged that at 93% effectiveness, it’s possible Natural Cycles could cause some unwanted pregnancies.

“As our user base increases, so will the amount of unintended pregnancies coming from Natural Cycles app users, which is an inevitable reality,” the spokesman said. He added, however, that Natural Cycles is “clinically proven” and should ultimately “decrease the unwanted pregnancy rates” around the world.