Base Infertile Pattern (BIP)

By RRM Academy Reviewed by Dr. Naomi Whittaker, MD, Board-Certified OBGYN, MIGS, NFPMC, FCI Updated May 14, 2026

The Base Infertile Pattern (BIP) is a woman's individual baseline of dryness or unchanging, featureless discharge that persists across consecutive days in the pre-Peak phase, during which conception is unlikely.¹

The BIP concept originated in the Billings Ovulation Method. Because many women cannot apply a simple dry-day rule, the Billings Ovulation Method teaches users to identify their personal baseline over several consecutive cycles. The BIP is not a single observation. It is an established, repeating pattern. Once confirmed, any day that matches the BIP is treated as infertile. Any departure from it marks the Point of Change and signals the opening of the fertile window.

This matters especially for women who carry continuous or unchanging mucus across much of their mucus cycle: those who are postpartum, breastfeeding, transitioning off suppressive medications, or moving through perimenopause. For these women, standard fertile-window identification fails. The BIP restores interpretive clarity by anchoring the fertile window to a departure from their own baseline rather than to a fixed rule.

In the Creighton Model, a closely related concept applies under different nomenclature. In both systems, establishing the BIP requires observation across multiple cycles and instruction from a trained practitioner. The BIP is a tool for reading the body's own signal accurately, not for overriding it.

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.