Cooperative Progesterone Replacement Therapy (CPRT)

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

Cooperative Progesterone Replacement Therapy (CPRT) is a cycle-timed luteal-phase progesterone protocol developed by Dr. Thomas Hilgers as part of NaProTECHNOLOGY, designed to support the corpus luteum's natural output without suppressing ovulation in subsequent cycles. The standard protocol uses oral micronized progesterone (sustained-release, 200 mg at bedtime) beginning on Peak +3 and ending on Peak +12, or at the onset of menses. Timing is determined by the woman's Peak Day as identified through CrMS charting.⁷⁸

CPRT is Hilgers' formal clinical alternative to continuous progestin regimens. It targets the specific window when progesterone is needed, then steps back. The corpus luteum is supported, not replaced. This distinction matters: continuous progestins suppress the next cycle's ovulatory sequence. CPRT does not.

Clinical indications include Type I, II, and III luteal phase deficiency, premenstrual syndrome with documented luteal hormone deficit, and recurrent early pregnancy loss with luteal insufficiency. Dosing is titrated against serial post-Peak progesterone levels drawn at Peak +5, +7, and +9. CPRT always uses isomolecular progesterone, not synthetic progestins.

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.