Billings Ovulation Method

The Billings Ovulation Method (BOM) is a method which women use to monitor their fertility, by identifying when they are fertile and when they are infertile during each menstrual cycle. Users pay attention to the sensation at their vulva, and the appearance of any vaginal discharge. This information can be used to achieve or avoid pregnancy during regular or irregular cycles, breastfeeding, and peri-menopause. Described by the World Organisation of the Ovulation Method Billings (WOOMB) as "Natural Fertility Regulation", this method may be used as a form of fertility awareness or natural family planning, as well as a way to monitor gynecological health.

In trials method related pregnancy rates have ranged between 0% to 2.9%. In a recent trial in China 992 couples using the Billings Method were compared to 662 couples using the IUD. The method-related pregnancy rate amongst Billings users was zero and the total pregnancy rate was 0.5%. In studies up to the 1980s teaching related pregnancies ranged between 0% to 6%. Total pregnancy rates vary between 1 and 25%. Reasons for a higher total pregnancy rate include misunderstanding the method, risk taking, ambivalence toward pregnancy, and deciding to become pregnant.

John Billings developed the method as a form of natural family planning in accordance with his religious faith. He was recognized with a Papal knighthood in life, and condolences for his death were given by the Pope. Billings strove to raise awareness of the significance of cervical mucus to fertility to all people, regardless of their religion.

Thomas Hilgers later created the Creighton Model FertilityCare System as a variation of the Billings method. While Hilgers describes his method as a "standardization" of the BOM, Billings and his wife disputed this claim in a position paper.