Premenstrual Bleeding (PMB)

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

Premenstrual Bleeding (PMB) is a Creighton Model biomarker consisting of brown spotting or light bleeding that appears before the onset of true menstrual flow, on days that should be post-Peak infertile days.¹

A healthy menstrual cycle builds toward flow and then tapers: the pattern reflects a corpus luteum that maintained adequate progesterone support through the post-Peak phase and then regressed cleanly. PMB breaks that pattern. Spotting before the red flow begins signals that the endometrium started breaking down before the corpus luteum finished its work. The most common underlying cause is progesterone deficiency, specifically a corpus luteum that failed to sustain its output long enough.²¹ Adenomyosis, uterine polyps, and fibroids can also produce this pattern, as can inflammatory conditions of the endometrium.³⁴⁵

PMB matters beyond cycle tracking. Premature endometrial breakdown is associated with difficulty conceiving and with early pregnancy loss. A Creighton Model chart makes PMB visible and repeatable across cycles. A single episode of premenstrual spotting may be a normal variation. A recurring pattern of PMB on a well-kept fertility chart is a signal of luteal phase insufficiency or structural pathology that warrants investigation.

NaProTechnology-trained clinicians use PMB alongside cycle-timed hormone measurements and ultrasound findings to identify the underlying cause. The goal is to restore normal luteal function rather than mask the pattern.

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.