The researchers say that reliable independent data on most of the systems used are still not available and that monitors differ enormously in price and effectiveness.
About 10-15 per cent (but with a very high estimated number of unknown cases) of women of reproductive age in Europe use variations of natural family planning methods and an estimated 30-40 per cent rely on some type of menstrual cycle monitor to detect the fertile 'window' in their menstrual cycle, usually for contraceptive purposes, but sometimes to optimise their chances of conception.
"If a couple are going to rely on these monitors, especially for contraception, then it is extremely important that they have reliable information about the effectiveness and accuracy of the different systems," said lead investigator emeritus Professor Guenter Freundl, gynaecological endocrinologist and senior partner at the Department of Reproductive Medicine and Gynaecological Endocrinology at Staedtische Kliniken Dsseldorf gGmbH, Frauenklinik Benrath, Dsseldorf.
The researchers have developed a method of testing the monitors by devising a QI (quality index). The days predicted as fertile by each of the systems were compared with the fertile time revealed by ultrasound scans and the detection of the surge of LH (luteinizing hormone) in the urine and basic daily conception probabilities. The resulting attributed QI ranges from zero to one, with small values indicating a good method for preventing a pregnancy and a value close to one being close to 'no method at all'. Six monitors were tested plus the symptothermal method (STM) of natural family planning (NFP) relying on a woman's own observations.
Contact: Margaret Willson
European Society for Human Reproduction and Embryology