Natural Cycles, an app that bills itself as a contraceptive and fertility tracker, has again found itself the target of regulatory investigation due to claims made in its advertisements.

According to the Guardian, the UK’s Advertising Standards Authority has kicked off a formal investigation into the Swedish company after receiving three complaints regarding the app and its paid advertising on Facebook. Specifically, a spokesperson for the group told the publication that the ad’s inclusion of language describing Natural Cycles as a clinically tested contraceptive would require “robust substantiation” before making such a claim.

Cofounded by Dr. Elina Berglund, a nuclear physicist who worked with CERN to find the Higgs Boson particle, and her husband Dr. Raoul Scherwitzl, Natural Cycles is a subscription service that includes an app and a basal thermometer. By taking their temperature in the morning and submitting additional information about their cycle, the app’s algorithm generates insights about the user’s daily fertility. The product is CE certified as a contraceptive in Europe, and raised $30 million in funding last November.

A spokesperson for Natural Cycles told the Guardian that the investigation is in regard to an ad that ran in 2017, and that the company has accepted draft recommendations from the advertising regulator. MobiHealthNews has reached out to the company for confirmation, and will update this story with any response.

Natural Cycles has been in hot water before. Earlier in the year, Södersjukhuset hospital in Stockholm, Sweden reported the system to Sweden’s Medical Products Agency (MPA) after it found that 37 women among 668 had experienced an unplanned pregnancy while using the app. Natural Cycles contested the claims against its effectiveness, noting that these cases translated to a roughly 95 percent success rate, which exceded the 93 percent success rate advertised by the company.

This investigation was exasperated just a few weeks later when the company released an erroneous announcement that the MPA had closed all individual reports related to the cases cited by Södersjukhuset hospital. Hours later, The Verge reported that the MPA has only concluded the first step of its investigation, and had decided “to escalate the ongoing market surveillance investigation to review parts of the documentation that was compiled as a justification for the CE mark certification.” MPA’s investigation is currently ongoing.