More than 50 women in Sweden who said they used the Natural Cycles app as contraception ended up pregnant and reported their cases to the Medical Product Agency, according to a statement from Natural Cycles. The app, a certified contraceptive in Europe, has about the same failure rates as the pill, but only under certain circumstances, according to experts. "Natural methods, when used correctly, are very very effective," Richard J. Fehring, professor, and director of the Marquette University College of Nursing Institute for Natural Family Planning, told International Business Times. The Natural Cycles app uses an algorithm to calculate the days a woman is fertile and therefore most likely to get pregnant and when used properly, it claims to be about as effective as the pill. The app requires that users take their temperature each morning and input it into the app, then after some calculations, the app says whether users are "not fertile," or should "use protection."