Asmr mullerian anomaly classification
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ASRM mullerian anomaly classification types AFS American Society Reproductive Medicine
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I now have sufficient information to give a thorough answer. Here is the complete ASRM/AFS Mullerian Anomaly Classification:
ASRM/AFS Classification of Mullerian Anomalies
There are two versions in current use: the original AFS 1988 classification (7 numbered classes, still widely referenced) and the updated ASRM 2021 classification (9 descriptive categories). The term "ASRM classification" technically refers to the 2021 update, but the 1988 system is so embedded in clinical teaching that it is often called "AFS/ASRM" interchangeably.
AFS 1988 Classification (7 Classes)
Based on Buttram and Gibbons 1979, originally published by the American Fertility Society.
| Class | Anomaly | Key Features |
|---|---|---|
| I | Mullerian agenesis / hypoplasia | Subtypes: (a) vaginal, (b) cervical, (c) fundal, (d) tubal, (e) combined. Mayer-Rokitansky-Kuster-Hauser (MRKH) syndrome is the prototype. |
| II | Unicornuate uterus (~15%) | One Mullerian duct fails to develop. Subtypes: (a) communicating rudimentary horn with endometrium, (b) non-communicating horn with endometrium, (c) horn with no cavity, (d) no contralateral horn at all. |
| III | Uterus didelphys (~7.5%) | Complete failure of lateral fusion - two separate uterine horns, two cervices. Often associated with longitudinal vaginal septum. |
| IV | Bicornuate uterus (~25%, 2nd most common) | Partial fusion failure at the uterine fundus with indentation of the serosa. Subtypes: (a) complete - division to the external os (bicornuate bicollis), (b) partial - not extending to the internal os (bicornuate unicollis). |
| V | Septate uterus (~45%, most common) | Normal external contour, but a fibromuscular septum divides the cavity. Subtypes: (a) complete (down to internal or external os), (b) partial (subseptate). Clinically significant - associated with the highest miscarriage rates. |
| VI | Arcuate uterus | Slight indentation of the uterine fundus. Near-normal variant; most authors consider it a minor anatomical variant with minimal reproductive impact. |
| VII | DES-related uterine abnormalities | Diethylstilbestrol (DES) exposure in utero. T-shaped uterine cavity, hypoplasia, irregular borders. |
Memory aid: "All Unicorns Dine Better - Some Always Deviate"
(Agenesis, Unicornuate, Didelphys, Bicornuate, Septate, Arcuate, DES)
ASRM 2021 Classification (MAC2021) - 9 Descriptive Categories
The 2021 update by the ASRM Task Force expanded the system to include cervical and vaginal anomalies, removed numbered classes, and added more precise diagnostic criteria. The official ASRM 2021 paper is the authoritative source.
- Mullerian agenesis - with or without unilateral/bilateral atrophic uterine remnants, with or without functioning endometrium
- Cervical agenesis - new separate category (was lumped under Class I in AFS)
- Unicornuate uterus - with or without contralateral rudimentary hemiuterus, with or without functioning endometrium
- Uterus didelphys - two hemiuteri with non-fused or duplicated cervix
- Bicornuate uterus - partially fused bodies due to indentation of the serosa
- Septate uterus - with more precise diagnostic criteria to distinguish from bicornuate
- Longitudinal vaginal septum (LVS) - new dedicated category
- Transverse vaginal septum - new dedicated category
- Complex anomalies - anomalies that don't fit neatly into a single category
Key Differences: AFS 1988 vs ASRM 2021
| Feature | AFS 1988 | ASRM 2021 |
|---|---|---|
| Number of categories | 7 (numbered classes) | 9 (descriptive terms, no numbers) |
| Cervical anomalies | Subsumed under Class I | Separate category |
| Vaginal anomalies | Not classified | Two dedicated categories (LVS, transverse septum) |
| Arcuate uterus | Class VI | Redefined - clearer criteria distinguishing from normal |
| DES-related | Class VII | Subsumed under complex anomalies |
| Complex anomalies | Poorly handled | Explicit dedicated category |
| Diagnostic criteria | Vague | More precise (esp. septate vs bicornuate) |
Clinical Pearls
- Septate uterus (Class V / Category 6) is the most common anomaly (~45%) and has the worst reproductive outcomes (highest miscarriage rate). It is also surgically correctable by hysteroscopic metroplasty.
- Key distinction - Septate vs Bicornuate: The external uterine contour is the differentiating feature. Septate = normal/convex outer contour; Bicornuate = concave outer contour (fundal indentation >10 mm). MRI or 3D ultrasound is needed to assess both internal and external contour simultaneously.
- Unicornuate uterus with non-communicating rudimentary horn carrying endometrium is a surgical emergency risk - endometriosis, hematometra, and ectopic pregnancy can occur.
- Renal anomalies coexist frequently with Mullerian anomalies (due to shared mesonephric duct proximity) - always image the kidneys. Unicornuate uterus has the highest rate of associated renal anomalies (~40%).
- Uterus didelphys paradoxically has better reproductive outcomes than the septate uterus.
- ESHRE/ESGE 2013 is another widely used alternative classification (especially in Europe), but tends to overdiagnose septate uterus compared to ASRM 2021.
Embryological Basis
Mullerian (paramesonephric) duct anomalies arise from three types of developmental failure:
- Failure of development (agenesis/hypoplasia) - Classes I, II
- Failure of lateral fusion (the two ducts don't fuse) - Classes III, IV
- Failure of resorption of the midline septum after fusion - Class V
Sources: Radiopaedia AFS Classification | ASRM 2021 MAC paper (PMC) | Berek & Novak's Gynecology
Asrm 2021 classification with categories
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ASRM MAC2021 mullerian anomaly classification all subcategories detailed categories
I now have comprehensive data from the official ASRM MAC2021 printable PDF and manuscript. Here is the full detailed breakdown:
ASRM Mullerian Anomalies Classification 2021 (MAC2021)
Published in Fertility and Sterility, Vol. 116, No. 5, November 2021. The official ASRM MAC2021 manuscript is the authoritative source.
MAC2021 has 9 categories identified by descriptive terminology (no longer numbered). Each category has 5 educational elements: Overview, Presentation, Diagnosis, Management, and Imaging.
Category 1: Mullerian Agenesis
Failure of Mullerian duct development - absent or rudimentary uterus and upper vagina (MRKH syndrome prototype).
Subcategories:
- Mullerian agenesis - complete absence, no uterine tissue
- Mullerian agenesis with R/L atrophic uterine remnant - small non-functioning uterine bud present
- Mullerian agenesis with functional endometrium - remnant with active endometrium (can cause cyclical pain/hematometra)
Category 2: Cervical Agenesis
New dedicated category in 2021 (was previously lumped under Class I agenesis in AFS 1988). Absent or severely hypoplastic cervix with a normally formed uterine body.
Subcategories:
- Cervical agenesis - complete absence of the cervix
- Distal cervical agenesis - distal portion of cervix absent, proximal portion present
Category 3: Unicornuate Uterus
One Mullerian duct fails to develop normally. Single uterine horn, single tube, single cornu.
Subcategories:
- R/L unicornuate uterus - solitary horn, no contralateral structure
- R/L unicornuate with R/L distal atrophic uterine remnant - small non-functioning contralateral bud
- R/L unicornuate with R/L distal uterine remnant with functional endometrium - non-communicating horn with active endometrium (risk of hematometra, ectopic, endometriosis)
- R/L unicornuate with R/L associated atrophic uterine remnant - variant positioning
- R/L unicornuate with R/L uterine horn communicating at level of cervix - communicating tract at cervical level
Category 4: Uterus Didelphys
Complete failure of lateral fusion of the two Mullerian ducts. Two completely separate hemiuteri, each with its own cervix.
Subcategories:
- Uterus didelphys - two hemiuteri, duplicated cervix, no vaginal septum
- Uterus didelphys +/- longitudinal vaginal septum of variable length - with or without longitudinal vaginal septum (most common associated finding)
- Uterus didelphys and obstructed R/L hemivagina - one vaginal canal obstructed (Herlyn-Werner-Wunderlich syndrome - associated with ipsilateral renal agenesis)
Category 5: Bicornuate Uterus
Partial fusion failure at the fundus. Two uterine horns with serosal indentation >1 cm. External contour is concave/indented.
Subcategories:
- Bicornuate uterus - standard partial fusion failure, single cervix
- Bicornuate uterus with R/L communicating tract - a tract connecting the two horns
- Bicornuate bicollis - complete division extending to two cervices
- Combined bicornuate septate uterus - bicornuate externally + internal septum
Key diagnostic criterion: Serosal indentation >1 cm distinguishes bicornuate from septate/arcuate.
Category 6: Septate Uterus
Normal external uterine contour (convex or flat fundus) with an internal fibromuscular septum. Most common Mullerian anomaly (~45%).
Subcategories:
- Partial septate uterus - septum does not reach the internal os; septum length >1 cm, angle <90°
- Normal / arcuate uterus - indentation ≤1 cm, angle >90° (considered normal variant)
- Complete septate uterus with duplicated cervices and longitudinal vaginal septum
- Complete septate uterus with septate cervix and longitudinal vaginal septum
- Robert's uterus - complete septum with one blind/obstructed hemicavity (rare complex variant)
Key diagnostic criteria (MAC2021):
- Septum: length >1 cm AND angle <90°
- Arcuate/Normal: indentation ≤1 cm AND angle >90° These criteria differ from ESHRE/ESGE (which uses a lower threshold and overdiagnoses septate uterus).
Category 7: Longitudinal Vaginal Septum (LVS)
New dedicated category. A vertical septum dividing the vagina partially or completely along its length.
Subcategories:
- Longitudinal vaginal septum of variable length - isolated LVS without uterine anomaly
- Longitudinal vaginal septum of variable length and uterus didelphys - combined with didelphys
- Obstructed R/L hemivagina and uterus didelphys - one side obstructed (Herlyn-Werner-Wunderlich)
- Longitudinal vaginal septum of variable length and complete septate uterus with duplicated cervix
Category 8: Transverse Vaginal Septum
New dedicated category. A horizontal membrane across the vaginal lumen at varying levels (upper, mid, or lower vagina). Causes outflow obstruction (hematocolpos, hematometra).
Subcategories:
- Mid vaginal septum - septum at mid-vaginal level
- Distal vaginal agenesis - lower vaginal segment absent (most obstructive)
Category 9: Complex Anomalies
Anomalies that don't fit neatly into a single category, or have combined elements from multiple categories. Catches the "unclassifiable" cases that were a limitation of the AFS 1988 system.
Summary Table
| Category | Anomaly | Key Feature | New in 2021? |
|---|---|---|---|
| 1 | Mullerian agenesis | Absent/rudimentary uterus + vagina | No (expanded) |
| 2 | Cervical agenesis | Absent cervix, uterus present | Yes |
| 3 | Unicornuate uterus | Single horn | No (expanded) |
| 4 | Uterus didelphys | Two separate uteri + cervices | No (expanded) |
| 5 | Bicornuate uterus | Serosal indentation >1 cm | No (criteria clarified) |
| 6 | Septate uterus | Normal contour, internal septum >1 cm, angle <90° | No (criteria redefined) |
| 7 | Longitudinal vaginal septum | Vertical vaginal wall | Yes |
| 8 | Transverse vaginal septum | Horizontal vaginal obstruction | Yes |
| 9 | Complex anomalies | Combined/unclassifiable | Yes |
Key Points About MAC2021
- No numbered classes - descriptive names only (unlike AFS 1988)
- Arcuate uterus is no longer a separate category - it is now classified as normal (indentation ≤1 cm, angle >90°)
- DES-related anomalies are subsumed under complex anomalies
- Cross-referencing allowed - vaginal anomalies in particular may appear in >1 category
- Interactive digital tool available at asrm.org/asrm-academy/asrm-academy-on-the-go/asrm-mac-tool with imaging examples in MRI, ultrasound, and HSG
- Associated anomalies (renal, skeletal) are incorporated - always image kidneys when a Mullerian anomaly is found
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