Fertility-Focused Intercourse (FFI)

By RRM Academy Reviewed by Dr. Naomi Whittaker, MD, Board-Certified OBGYN, MIGS, NFPMC, FCI Updated May 7, 2026

Fertility-focused intercourse (FFI) is Hilgers' term for intercourse timed by CrMS biomarker observations to coincide with the identified fertile window, particularly Peak Day and the three preceding days.⁸³

In the landmark 1992 Hilgers, Daly, Prebil, and Hilgers cohort of 50 apparently-fertile couples, FFI produced cumulative pregnancy rates of 76% in cycle 1, 90% by cycle 3, and 98% by cycle 6.⁸³ These are the most-cited CrMS achievement statistics, and they derive from a single clinical principle: when the fertile window is identified accurately, conception follows for nearly all couples without further intervention.

FFI reframes the clinical question. The standard approach asks whether a couple's biology can support pregnancy. FFI asks whether the fertile window was actually used. For couples labeled with undiagnosed infertility, accurate fertile-window identification through CrMS charting is frequently the missing variable.

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.