The Endometriosis Fertility Index (EFI) is a tool used to assess the potential fertility of women with endometriosis.

The EFI is a scoring system that takes into account various factors that can affect fertility in women with endometriosis, including the woman’s age, the severity and location of the endometriosis, the presence of adhesions or scar tissue, and the results of any previous fertility treatments. The EFI score ranges from 0 to 10, with higher scores indicating a better chance of achieving pregnancy.

The EFI can be a useful tool for both doctors and patients in making decisions about fertility treatments for women with endometriosis. However, it is important to note that the EFI is just one of many factors that should be considered when making decisions about fertility treatment, and that individual outcomes may vary based on a wide range of factors.

The Endometriosis Fertility Index (EFI) is calculated using six factors, each of which is assigned a score based on specific criteria. The scores for each factor are then added together to give the overall EFI score. The EFI score can be used to predict natural pregnancy rates. Here are the six factors and their corresponding scores:

Medical History

1. Age

  • Age 35 or younger = 2 points
  • Age 36 to 39 = 1 point
  • Age 40 or older = 0 points

2. Years Infertile

  • Less than or equal to 3 years = 2 points
  • More than 3 years = 0 points

3. Previous Pregnancies

  • Previous pregnancy = 1 point
  • No previous pregnancies = 0 points

Surgical Factors

4. Least Function (LF) Score

This is a little complicated to calculate and should be done by your surgeon.

  • If LF score = 7-8 (high score) = 3 points
  • If LF score = 4-6 (moderate score) = 2 points
  • If LF score = 1-2 (low score) = 0 points

5. AFS Endometriosis Score

  • AFS Endometriosis Lesion Score < 16 (Stages 1 or 2) = 1 point
  • AFS Endometriosis Lesion Score ≥ 16 (Stages 3 or 4) = 0 points

6. AFS Total Score

  • AFS total score < 71 = 1 point
  • AFS total score ≥ 71 = 0 points

EFI = Total Medical History Factors + Total Surgical Factors

To calculate the EFI, the score for each of these six factors is added together. The maximum possible score is 10, and the minimum possible score is 0. A higher EFI score indicates a better chance of achieving pregnancy, while a lower score indicates a lower chance of success.



Matt is an NHS Consultant in Newcastle with over ten years of experience. His PhD research into subfertility and miscarriage involved developing a clinical trial and patient engagement.