What is a good antral follicle count (AFC) for in vitro fertilization (IVF)?

Good Antral Follicle Count for IVF

An antral follicle count (AFC) of 8-15 is considered optimal for IVF success, while an AFC below 5 indicates diminished ovarian reserve that significantly increases the risk of poor response to stimulation and miscarriage.

Understanding Antral Follicle Count in IVF

Antral follicle count (AFC) is a critical parameter in assessing ovarian reserve prior to in vitro fertilization (IVF). It provides valuable information about:

1. Potential response to ovarian stimulation
2. Expected number of oocytes that can be retrieved
3. Likelihood of IVF success
4. Risk of miscarriage

AFC Measurement and Interpretation

AFC is typically measured via transvaginal ultrasound (TVUS) during the early follicular phase of the menstrual cycle. According to clinical guidelines 1:

• Method: TVUS is the preferred approach for accurate follicle counts
• Timing: Early follicular phase (days 2-5 of cycle)
• Follicle size: Follicles measuring 2-9 mm in diameter are counted
• Interpretation thresholds:
  • <5 follicles: Diminished ovarian reserve
  • 5-7 follicles: Low-normal reserve
  • 8-15 follicles: Optimal reserve
  • >25 follicles: Suggestive of polycystic ovarian morphology

AFC and IVF Outcomes

Prediction of Ovarian Response

AFC is superior to basal FSH in predicting ovarian response to stimulation 2. A meta-analysis demonstrated that AFC performs significantly better than basal FSH in predicting poor ovarian response during IVF cycles.

• Poor response risk:
  • AFC ≤4: High risk of poor response
  • AFC 5-7: Moderate risk
  • AFC ≥8: Lower risk of poor response

AFC and Oocyte Yield

A 2024 study found that among patients with discordant ovarian reserve markers 3:

• AFC ≥6 had 77% sensitivity for predicting non-poor ovarian response (≥4 oocytes retrieved)
• AFC was a stronger predictor of oocyte yield than AMH when markers were discordant

Miscarriage Risk

AFC has important implications for pregnancy outcomes. According to a 2021 meta-analysis 1:

• Women with low AFC have significantly higher miscarriage rates compared to those with medium or high AFC
• Low AFC vs high AFC: OR 3.42 (95% CI, 1.13-10.32; P=0.03)
• This relationship appears independent of age

Clinical Approach to AFC in IVF Planning

Stimulation Protocol Modifications

A worldwide survey of IVF centers found that 89.7% of respondents modify their IVF stimulation protocols based on AFC 4. This demonstrates the clinical importance of this measurement.

Minimum AFC Thresholds for IVF

The same survey revealed variation in minimum AFC requirements for initiating an IVF cycle 4:

• 46.1% of centers use ≥3 antral follicles as their threshold
• 39.9% require 4-5 follicles
• 14.0% set higher thresholds

Age and AFC Interaction

The combination of age and AFC provides better predictive value than either parameter alone 5:

• AFC primarily influences oocyte quantity
• Age primarily affects oocyte quality
• AFC ≤7 or age ≥38 years with AFC ≤10 indicates diminished ovarian reserve

Important Caveats and Considerations

1. AFC limitations: While AFC predicts ovarian response well, it has poor performance in predicting pregnancy rates 2.

2. Quality vs. quantity: AFC primarily predicts oocyte quantity but not quality or embryo development potential 6.

3. Technical considerations:

   • High-frequency transvaginal probe (≥8 MHz) is recommended for accurate counts 1
   • Transabdominal ultrasound is less reliable for AFC assessment
   • MRI may be considered when ovaries cannot be adequately visualized by ultrasound 1

4. Discordant markers: When AFC and AMH are discordant, AFC appears to be the more reliable predictor of ovarian response 3.