Obstetrics and Neonatology

EFI Calculator: Endometriosis Fertility Index (Simplified)

Predicts spontaneous pregnancy after endometriosis surgery (Adamson-Pasta, simplified)

Primary source: Adamson GD, Pasta DJ. Fertil Steril 2010; 94(5): 1609-1615 (упрощённая агрегация)

Aleksandr A. Aulov, MD, internal medicine Last clinical review: April 28, 2026

Online calculation

Duration of infertility

Pregnancy history

Endometriosis stage (rASRM)

Least Function score (aggregated)

Based on surgical findings: normal / mild decrease / moderate / severe / absent function

About this score

The EFI (Endometriosis Fertility Index, Adamson GD, Pasta DJ, Fertil Steril 2010) is a simplified scale for predicting pregnancy after surgical treatment of endometriosis. It incorporates preoperative history (age, duration of infertility, prior pregnancies) and intraoperative findings (rASRM score and functional assessment of the fallopian tubes and ovaries using the Least Function system).

The scale ranges from 0 to 10. Low values (0–4) correspond to a ~10% probability of spontaneous pregnancy within 3 years after surgery; 5–6, ~30%; 7–8, ~50–60%; 9–10, up to 70%. Validation studies show EFI predicts pregnancy better than rASRM stage alone, because it incorporates functional assessment and history.

ESHRE 2022 guidelines on endometriosis list EFI as a recommended tool for prognosis and counseling of patients after surgery. EFI is used to decide whether to pursue natural conception attempts (EFI ≥ 7) or proceed directly to ART (EFI ≤ 4).

When to use

After surgical treatment of endometriosis, to predict the likelihood of pregnancy.
Counseling the patient and couple, to support the choice between expectant management and ART.
Documenting the clinical rationale for referral to IVF.
Inclusion in clinical research on endometriosis.

Clinical example

Case

A 32-year-old woman with 3 years of infertility and one prior term pregnancy. Laparoscopy: extensive endometriosis, rASRM 28 points (stage III), right tube patent, left tube partially blocked, both ovaries with endometriomas, functional after cystectomy but with reduced reserve.

Calculation

Age ≤ 35 (2) + duration of infertility 3 years (1) + prior pregnancy (1) + Least Function 5 (2) + rASRM 16–70 (1) + endometriosis score (per formula) ≈ EFI 6.

Interpretation and management

EFI 6 indicates a moderate prognosis for spontaneous pregnancy (~30% over 3 years). Management: discuss two strategies: (1) natural conception attempts for 6–12 months with ovulation monitoring; (2) ART (IVF), especially if ovarian reserve is reduced (AMH, AFC). If pregnancy is a high priority and age is closer to 35, earlier ART is favored. In parallel, discuss semen analysis with the partner.

Limitations and cautions

Requires surgical data; not applicable in patients without laparoscopy.
Does not account for male factor infertility; concurrent semen analysis is required.
Accuracy is lower in women over 40 years, where age dominates independently of EFI.
Depends on the operating surgeon's experience in assessing tubal and ovarian function.

Frequently asked questions

What is the Least Function score?

A functional assessment of the fallopian tube, fimbriae, and ovary, each scored on a 4-point scale. The worse side is used. Total range 0–8.

At what EFI is immediate ART recommended?

EFI ≤ 4: most protocols recommend proceeding to ART. EFI 5–6: decided individually based on age, duration of infertility, and psychosocial factors.

Can EFI be calculated without surgery?

No. EFI requires intraoperative rASRM and LF data; there is no substitute without laparoscopy. For a general prognosis, age, duration of infertility, and AMH are used.

Does EFI change over time?

The age component can change (shifting into a new category). Duration of infertility after surgery also affects the score; each additional year without pregnancy lowers the prognosis.

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Aleksandr A. Aulov Physician, internal medicine, Sechenov School — independent medical education platform. Calculators are compiled from the original publications and current clinical guidelines. Interpretation thresholds follow the source study unless stated otherwise.

This calculator is intended for healthcare professionals. Do not use it for self-diagnosis or self-treatment. Management decisions are made by the treating clinician based on the full clinical picture of the individual patient.