Women who use menstrual cycle monitors to detect their fertile times of the month should research their choices carefully because some methods are much more reliable than others.
German researchers estimate 10 percent to 15 percent of women of reproductive age in Europe use variations of natural family planning methods and an estimated 30 percent to 40 percent rely on some type of menstrual cycle monitor to detect their fertile times for either conception or contraceptive purposes. The days predicted as fertile by each of the monitoring systems were compared to the fertile time revealed by ultrasound scans, the detection of the surge of luteinizing hormone -- a hormone that controls the length and sequence of the menstrual cycle -- and basic daily conception probabilities.
Researchers found systems using a mini-microscope, which rely on the user recognizing "ferning" patterns from small samples of saliva or cervical mucus are highly susceptible to producing false negatives. The "ferning" patterns indicate fertility, so if a woman does not see a "ferning" pattern, she may incorrectly surmise she's not likely to conceive on that day. Even the most accurate of the three systems tested was wrong at least half of the time and the worst one was wrong nearly three-quarters of the time. The researchers say these methods should not be considered for further efficacy testing since they were typically inaccurate.
However, researchers were optimistic about the symptothermal method, which relies on a woman's own observation of two indicators of fertility -- changes in her basal body temperature and in her cervical mucus patterns -- plus some calculation rules. This method did not give the women involved in the study any false negatives.
Other methods such as a monitor that tests hormone levels in urine and a mini-computer that records and stores changes in basal body temperature also worked reasonably well.
Thus researchers concludes that the symptothermal method of [natural family planning] that relies on a woman's own observations proved to be the most effective of the natural family planning methods. The temperature computers scored the upper range of reliability and the hormonal computer in the medium range. But, the mini-microscopes had a very low estimated efficacy.
Hence there is an "urgent need" to test the systems that met their basic quality index standards.