A Facebook ad for the smartphone app Natural Cycles promising a “highly accurate” birth control method has been banned for making misleading claims by the UK’s advertising regulatory body today.

The Advertising Standards Authority (ASA) investigated the claims made in a Facebook ad after it received complaints about the app. The ad said the app was clinically tested and highly accurate, but the ASA’s investigation found that the ad exaggerated how effective the app is.

The words “clinically tested” and “highly accurate” together could be falsely interpreted by consumers to mean that Natural Cycles is an effective means of birth control that could replace other established birth control methods, said the ASA.

The Natural Cycles app, which costs $79.99 a year on Android and iOS, has been promoted as a birth control method that tracks a user’s cycle to say which days the user is fertile. To use it, you have to take your temperature every morning at the same time to track ovulation and menstrual cycles. (Smoking, drinking, and other activities can disrupt the temperature reading.) The app was approved by the US Food and Drug Administration this month and has been EU certified since February.

In January, Natural Cycles was reported to Swedish authorities by a women’s clinic, after 37 women visited the clinic for abortions after getting unwanted pregnancies using the app.

When the app is used correctly, only 10 out of 1,000 women who used the app for one year would become pregnant. This works out to a perfect-use effectiveness of 99 percent, which is the same perfect-use number as birth control pills. Still, perfect use of the Natural Cycles app has been notably uncommon. In evidence submitted to ASA, less than 10 percent of cycles were perfect-use.

The app’s typical-use effectiveness is lower: 68 out of 1,000 women become pregnant after using the app for a year, which works out to an effectiveness rate of 93 percent. That number suggests that the app beats condoms’ effectiveness rate, which is 82 percent in typical use, and that of hormonal birth control pills, which are 91 percent effective in typical use. The app isn’t as good as a patch or an IUD.

“The evidence did not demonstrate that in typical-use it was ‘highly accurate,’” the ASA wrote in its ruling to ban the Facebook ad. Natural Cycles responded in a statement that it respected the outcome of the investigation and that the ad was removed in mid-2017 as soon as the company was notified of the complaint.