Sonographic Classification of Ovulation Disorders (Hilgers Classification)

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

The Hilgers Sonographic Classification of Ovulation Disorders is an eight-category serial-ultrasound framework that characterizes the quality of the ovulatory event, distinguishing anatomically normal ovulation from six distinct pathological patterns and one anovulatory variant.

A positive ovulation predictor kit tells a woman that an LH surge occurred. It says nothing about whether the follicle matured adequately, ruptured fully, released the cumulus oophorus intact, or collapsed at a normal rate. Hilgers' classification, developed from serial periovulatory ultrasound, captures what actually happened at the follicle.⁷⁸

Normal ovulation requires a mature follicle of 1.90 cm or greater mean diameter, a positive cumulus oophorus sign, and complete rupture. Deviation from any criterion defines a disorder category. The eight categories are: anatomically normal ovulation; Luteinized Unruptured Follicle Syndrome (LUF); Mature Follicle with Absent or Retained Cumulus; Immature Follicle Syndrome (mean diameter below 1.90 cm at rupture); Partial Rupture Syndrome (collapse of 7.5 mm or less over 24 hours); Delayed Rupture Syndrome (rupture spread across 48 hours); Afollicularism (no follicle reaches dominance); and Empty Follicle Syndrome (absent cumulus oophorus on ultrasound). Each category carries distinct downstream fertility implications and maps to specific restorative interventions. A follicle maturation study is the ultrasound series used to generate this classification.

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.