There are a number of natural methods of fertility management, but only a few (notably, the Billings Ovulation Method (BOM), the Creighton Method (CrM) and the Sympto-Thermal Method (STM)) have been demonstrated to be consistently reliable in avoiding and also achieving a pregnancy. Unlike the old Rhythm Method (referred to on occasions as Catholic Roulette!), these modern methods of natural fertility management are very effective – more effective in fact, than some popular contraceptives, such as condoms and diaphragms. Natural methods also have the advantage of being free of physical side effects. See the appendix for a detailed overview of the various family planning methods.
Billings Ovulation Method (BOM)
Named after its developers, Drs John and Lyn Billings of Melbourne, this method teaches a couple how to identify the fertile and infertile days in a woman’s cycle by observing the changes in the cervical mucus. Mucus is secreted by specialized cells in the cervix immediately prior to and at the time of ovulation. The mucus can be felt and seen when it leaves the woman’s body at the vulva (i.e. the opening of the vagina). A couple using this method keeps a daily record of the woman’s vulval sensations as well as the colour and consistency of any mucus secretion. These observations allow the couple to determine when they are fertile (Fig. 2).A schematic illustration of a typical cycle showing the days of combined fertility (blue) and infertility. Ovulation is preceded by several days of fertile cervical mucus secretion (dark blue). Once ovulation occurs cervical mucus abruptly changes or disappears and basal (resting) body temperature rises. Intercourse on any day when there is fertile mucus present, or up to three days afterwards, is potentially fertile.
Creighton Method Fertility Care System (CrM)
This method is similar to the BOM, except that it involves a standardised and more detailed system for describing and recording the cervical mucus. The CrM is particularly helpful as a diagnostic tool in the detection of many gynaecological abnormalities.
Sympto-Thermal Method (STM)
This method incorporates the change in a woman’s body temperature following ovulation, and some other indicators, in addition to the cervical mucus symptom. The temperature change can be very useful in confirming the mucus observations.