Advertising on Facebook for an app that offers a natural alternative to contraception has been banned by the UK Advertising Standards Authority.
Allegations of being "very precise" and offering "a clinically tested alternative to other contraceptive methods" proved misleading.
The Swedish company behind the Natural Cycles app was warned not to overdo their effectiveness.
As a result, the company stated that it respects the result of the investigation.
She informed the BBC that she had removed the ad, which ran for about four weeks in mid-2017, as soon as she was informed of the complaint.
"We commit ourselves to being open and transparent in our communications to ensure our message is clear, and to provide women with the information they need to determine if Natural Cycles is right for them Advertising a strict approval process. "The company said in a statement.
"Natural Cycles has been independently evaluated by regulators in Europe and the US and validated on the basis of clinical data demonstrating its efficacy as a contraceptive method."
ASA said that the Facebook ad should no longer appear in its current form.
Natural Cycles requires women to measure their body temperature every day with a basal body thermometer and read it into the app, which also tracks the user's menstrual cycle.
The app uses an algorithm to determine a woman's daily fertility based on changes in basal body temperature.
Basal thermometers can detect a slight increase in temperature around the time of ovulation. Women will see a "use protection" warning during the fruitful days on the app.
Launched in 2014, the app now has more than 300,000 users paying a monthly or annual fee for the service.
It was invented by the Swedish nuclear physicist Elina Berglund Scherwitzl and her husband.
It has already been approved by the German testing and certification organization Tuv Sud for use as a medical device and can thus be used throughout the EU.
And recently, it received approval from the US Food and Drug Administration, which described it as an effective contraceptive method when used "carefully and correctly".
At the time, Terri Cornelison, deputy director of women's health at the FDA Center for Equipment and Radiological Health, said: "Women should know that no form of contraception works perfectly, so an unplanned pregnancy could still result in proper use Device."
When considering the complaint, which was filed by three people, the ASA took expert advice and reviewed three published papers based on the data collected from the app.
It was found that a distinction was made between the typical use of the app and the scenario of perfect use. It was assumed that the numbers submitted to the users were based on the perfect user rather than the typical user and that the system could not be described as very accurate for the latter.
It was also noted that the statement "very accurate", along with the claim "clinically tested alternative to contraceptive methods," gave the impression "that the app was a precise and reliable method of preventing pregnancies that could be used instead of another established birth control Methods ".
Natural Cycles told the ASA that the claim "clinically tested alternative to contraceptive methods" was a quote from the business insider news page.
But, it added, the claims were backed by scientific evidence, including clinical trials.
Separately, the app is being investigated by Sweden's Medical Products Agency (MPA), which has informed the BBC that it has received about 60 complaints of unwanted pregnancies as a result of using the app.
It will publish its conclusions next week.