Billings Ovulation Method

By RRM Academy Reviewed by Dr. Naomi Whittaker, MD, Board-Certified OBGYN, MIGS, NFPMC, FCI Updated May 13, 2026

The Billings Ovulation Method (BOM) is a mucus-only fertility awareness method developed by Australian physicians Drs. John and Evelyn Billings in the 1950s, based on the recognition that cervical mucus characteristics at the vulva change predictably across the cycle in response to estrogen and progesterone.¹ No thermometer, monitor, or instrument is required. BOM is taught through observation of sensation and appearance alone, making it one of the most globally accessible fertility awareness systems across varied cultural and resource settings.

Users observe and record daily the sensation of dryness, moisture, or slipperiness at the vulva, along with any visible mucus. As estrogen rises in the pre-ovulatory phase, mucus becomes more abundant, clearer, and increasingly slippery. The Peak Symptom marks the last day of this fertile-type mucus, corresponding closely to the time of ovulation.² Post-Peak rules then define the infertile phase. Teaching is provided through a network of certified Billings educators, with materials adapted to dozens of languages.

The World Health Organization supported multicountry field trials of BOM in the 1970s and 1980s to evaluate its effectiveness in diverse populations. Published effectiveness data support low method-failure rates when the method is correctly understood and applied.³ BOM is the foundational mucus-based method from which the Creighton Model FertilityCare System was later standardized; both methods share core mucus observation principles while operating as distinct systems with separate teaching networks and rule structures.

Among Fertility Awareness-Based Methods, BOM holds a distinct position as one of the oldest scientifically studied mucus-based systems, with a publication record dating to the 1970s and a clinical literature on mucus pattern interpretation that continues to inform modern FABM research.⁴

This content is for educational purposes only and does not constitute medical advice. Consult an RRM clinician or healthcare provider for guidance specific to your situation.