The Babycomp/Ladycomp (Valley Electronics Ltd., Eschenlohe, Germany) is an electronic device that combines the temperature method and calendar method for planning and preventing pregnancy by identifying the fertile and infertile phases of the menstrual cycle. In a retrospective clinical trial, the system was tested as a contraceptive aid. A total of 648 women from Germany and Switzerland have participated: 597 women with 10,275 months of use used the device for contraception. Thirty-three unplanned pregnancies were identified, giving a total pregnancy rate of 3.8 use effectiveness according to the Pearl Index. Six method-related pregnancies occurred, producing a method Pearl Index of 0.7. Calculating the cumulative pregnancy rates by life-table analysis, it was found that, after about one year of exposure, the probability of an unintended pregnancy was 5.3% (0.053), after 2 years it was 6.8% (0.068) and after about 3 years of exposure it was 8.2% (0.082). The mean length of the identified fertile period was 14.3 days with a standard deviation of 4.6 days in all cycles reported. The acceptance of the device by the woman and her partner was good. In fact, 21 of the 33 women who became pregnant would still recommend the device for further use (63.6%).