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A Swedish regulator closed its investigation into the FDA-cleared contraception app Natural Cycles Thursday, concluding that the despite a spate of unwanted pregnancies, the app’s “failure rate” matched the one the company laid out in its marketing materials.

But the investigation also highlighted an eyebrow-raising number: More than 660 people who used the app in Sweden reported unintended pregnancies between January and June of this year, according to the report released by the Swedish Medical Products Agency, known in Swedish as Läkemedelsverket.

That seemingly high number is still within the “typical use” failure rate of 6.9 percent because so many people are using the app in Sweden. More than 900,000 people around the world have downloaded Natural Cycles, according to the company’s website.


“There has been a lot of discussion about this investigation, and we hope that it will provide some reassurance to women to see eminent bodies like the Swedish MPA and the US FDA in alignment based on the strength of our clinical evidence,” Raoul Scherwitzl, the CEO of Natural Cycles, said in a press release. “We never doubted the effectiveness of our product since the number of reported pregnancies is monitored closely on a monthly basis.”

The Natural Cycles app works by measuring a patient’s resting temperature, or basal body temperature, which shifts when a person is ovulating due to surges in the hormone progesterone. The app uses those shifts to predict when a person should abstain from sex or use a different form of contraception.


Swedish regulators asked the company to clarify, within the app, the risk that a person using the app might get pregnant accidentally. The company said those changes were completed earlier this year, a press release from the company stated.

In Europe, the app is CE-marked. That means it falls in line with certain established regulations and standards for medical devices; it does not mean that national or European regulators reviewed the data.

The FDA cleared the app to prevent pregnancy in August. As part of that clearance, the agency reported that the app has a “typical use” failure rate of 6.5 percent.