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The Ovulation Method
Author: Richard Fehring, DNSc, RN

The Ovulation Method (OM)* of Natural Family Planning makes use of the observation of cervical mucus to determine fertility and infertility. This method was first developed by Drs. John and Evelyn Billings of Australia. Although several variations of OM exist, OM continues to be popularly referred to as the "Billings Method."

The careful observation and charting of the presence of cervical mucus on a day to day basis will ensure a couple success in achieving their family planning goal. When practiced each day, this observation will soon become part of normal daily hygiene.

Key words: Cervical Mucus Peak Day Daily Observation

*For further information on the Ovulation Method see, Evelyn Billings & Ann Westmore, The Billings Method, Controlling Fertility Without Drugs or Devices (1995), available from BOMA, USA, see p. 18.

A primary sign of a woman's fertility is cervical mucus. When an egg in a woman's body starts to mature, the hormone estrogen increases and stimulates the cells lining the cervical canal to produce mucus. Once estrogen stimulates these cells, cervical mucus will be felt by the woman. The result of this hormonal activity is generally described by women as a feeling or sensation of wetness. Mucus can also be observed by wiping the vulvar area from front to back with toilet tissue each time the woman goes to the bathroom. When mucus is present on the tissue, it can be picked up and observed.The woman must be consistent in daily sensing or observing the presence (or absence) of her mucus. During fertility, as the estrogen level rises, cervical mucus changes in consistency and quantity. The sensation also changes to one of slipperiness and greater lubrication, which the woman can notice as she goes about her normal daily routine. The last day of slippery mucus or a sensation of wetness is called Peak day. Ovulation occurs within 24 or 48 hours of the Peak.

After ovulation, estrogen levels start to drop off, progesterone levels increase and the cervical mucus becomes sticky and cloudy again and/or dry (see figure 2). The woman will experience a sensation of dryness. Once ovulation occurs the egg lives 12-24 hours. The fertile phase is from the beginning of the changing mucus pattern until the fourth day past Peak.

Achieving Pregnancy
If you wish to achieve pregnancy, obviously the best time to have intercourse is when the woman is fertile. The optimal time to achieve pregnancy (using cervical mucus as a sign) is the day(s) of the greatest quantity and quality of cervical mucus. Good quality mucus is stretchy, clear and gives the woman a sensation of lubrication.

Avoiding Pregnancy
Menstruation is a potentially fertile time since a woman can ovulate early in any cycle. If avoiding pregnancy is desirable, it is recommended that a couple abstain from intercourse during menses. In addition, because a woman will need to be alert for the on-set of mucus during the pre-ovulatory phase of the cycle, a couple must restrict intercourse to only the evening of every other dry day (that is, a day where no mucus was present and no sensation of wetness or slipperiness was felt by the woman).

Once cervical mucus has been observed, intercourse and all genital to genital contact must be avoided every day while mucus is present. During this time, the last day of mucus ( ) will have to be identified. Peak Day is identified as the last day of the most fertile sign, whether it is the last day of slippery, stretchy or blood tinged mucus or the last day of a lubricative, wet sensation. Peak Day cannot be reliably identified until the following day, when mucus undergoes a change under the influence of progesterone.

The Ovulation Method identifies the post-ovulatory phase of the cycle as beginning on the fourth day after the Peak of cervical mucus. This time of infertility will last up to the first day of menstruation. During this phase of the cycle, intercourse can occur any time of the day or night.


Richard Fehring, DNSc, RN, is Associate Professor and the Director of the Marquette University Institute for NFP, College of Nursing, Milwaukee, WI. Dr. Fehring is the Chairman of the Science and Research Committee for the American Academy of Natural Family Planning and has published on the science of NFP.