What is the Endometriosis Fertility Index (EFI)?

The Endometriosis Fertility Index (EFI)

The Endometriosis Fertility Index (EFI) is a simple, robust, and validated clinical tool that accurately predicts fertility outcomes for women following surgical staging of endometriosis, providing essential guidance for developing treatment plans for infertile women with endometriosis. 1

Definition and Purpose

The EFI is a scoring system developed to predict pregnancy rates in patients with surgically documented endometriosis who attempt non-IVF conception 2. Unlike the revised American Fertility Society (r-ASRM) classification which has limited predictive ability for pregnancy after surgery, the EFI was specifically designed to predict fertility outcomes 3, 4.

Components of the EFI Score

The EFI incorporates both historical factors and surgical findings:

1. Historical factors at time of surgery:

   • Age
   • Duration of infertility
   • Pregnancy history

2. Surgical factors:

   • Least function score: Assessment of functional status of fallopian tubes, fimbriae, and ovaries bilaterally after surgical intervention (most important component) 5
   • r-ASRM endometriosis lesion score
   • Total r-ASRM score

Scoring and Interpretation

• The EFI provides a numerical score that correlates with pregnancy probability
• Higher scores indicate better fertility prognosis:
  • Scores ≥6 are associated with significantly higher pregnancy rates 6, 4
  • Scores ≤5 indicate poorer fertility outcomes

Clinical Utility

• Predictive value: The EFI has superior predictive power for fertility outcomes compared to the r-ASRM classification system 4
• Treatment guidance:
  • Helps determine whether patients should attempt natural conception or proceed directly to assisted reproductive technologies
  • Patients with EFI scores ≥6 may reasonably attempt natural conception
  • Patients with lower scores (≤5) may benefit from earlier referral to IVF 5
• Timing considerations: Most spontaneous pregnancies (82.7%) occur within the first 12 months after surgery 6

Implementation in Clinical Practice

The World Endometriosis Society strongly recommends that all women with endometriosis for whom fertility is a future concern should have an EFI score calculated and documented in their medical records following surgical treatment 3, 1.

Advantages Over Other Classification Systems

• More predictive of fertility outcomes than r-ASRM classification 4
• Provides actionable information for clinical decision-making
• Validated in multiple populations 6, 5
• Helps avoid wasted time and ineffective treatments for patients with poor prognoses 2

Common Pitfalls and Caveats

• The EFI is only applicable after surgical evaluation and treatment of endometriosis
• It specifically predicts fertility outcomes but does not address pain symptoms or quality of life
• The World Endometriosis Society recommends using multiple classification systems together (r-ASRM, Enzian for deep endometriosis, and EFI) for comprehensive documentation 3

The EFI represents an important advancement in endometriosis management, moving beyond simple description of disease to providing prognostic information that directly impacts clinical decision-making for infertile women with endometriosis.