Menstrual Cycle Monitors Show Wide Variation in Accuracy

Some are wrong more than half the time

WEDNESDAY, Nov. 26, 2003 (HealthDayNews) -- Monitoring a woman's menstrual cycle is greatly effective, or not effective at all: it seems to depend on what type of monitoring is being done.

A new German study finds that more testing is needed to determine the accuracy of different menstrual cycle monitors used by couples practicing natural family planning. The report is published in the Nov. 27 issue of the journal Human Reproduction.

The report says that there is still no reliable independent data available on most of the cycle monitors, which differ greatly in price and effectiveness.

It's estimated that about 30 percent to 40 per cent of European women of reproductive age use some type of menstrual monitor to detect when they are fertile.

Most use the monitors as a form of birth control, but some also use them to improve their chances at getting pregnant.

The researchers tested a number of monitors in a study that included 62 women. The study found that three cycle monitors that use a mini-microscope to analyze samples of saliva or cervical mucus were wrong 51.8 per cent, 58 per cent, and 73.4 per cent of the time in pinpointing when a woman was in a non-fertile part of her cycle.

Monitors that used a mini computer to record and store body temperature data performed better, with 1.7 per cent, 4.7 per cent, and 7.5 per cent false negative readings.

Another monitor that tested hormone levels in urine recorded 20.8 per cent false negatives.

The researchers also tested the sympothermal method. This relies on a woman's own observations of fertility indicators -- changes in body temperature and in cervical mucus patterns, along with calculation rules. There were no false negatives for the 15 women who used this method, the study says.

More Information

Here's where you can learn more about birth control.

SOURCE: European Society for Human Reproduction and Embryology, news release, Nov. 26, 2003
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