Home / Calculators / Ovarian response / Follicle to oocyte index
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A calculator sees three or four figures. A specialist sees your history, your scans, your partner's results, and how you actually responded to treatment. If you're between cycles, changing clinics, or something in your results doesn't add up, a second opinion is the fastest way to find out whether anything would be done differently.
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These tools provide general information and are not a diagnosis or a substitute for assessment by a qualified clinician. Reference ranges and sources are stated on each calculator. Predictive estimates describe groups of people and cannot predict an individual outcome.
A calculator sees three or four figures. A specialist sees your history, your scans, your partner's results, and how you actually responded to treatment. If you're between cycles, changing clinics, or something in your results doesn't add up, a second opinion is the fastest way to find out whether anything would be done differently.
Free first consultation. No obligation to start treatment, and it doesn't affect your care at your current clinic.
Eggs retrieved relative to the follicles available.
Exact calculationArithmetic on the numbers you enter. If your inputs are right, this figure is right.
The follicle to oocyte index is eggs retrieved divided by antral follicle count. Below 50% is used in the POSEIDON framework as a marker of hyporesponse despite adequate reserve.
Source — FOI below 50% is used in the POSEIDON framework as a marker of hyporesponse despite adequate reserve.
Total collected
At baseline scan
That falls in the 50–100% band.
Your result of 79 % sits in the highlighted band. Bands are reference points used alongside clinical findings — not a diagnosis.
Within the range described as adequate in the POSEIDON literature.
FOI below 50% is used in the POSEIDON framework as a marker of hyporesponse despite adequate reserve.
Highlighted is the stage this measurement belongs to. It is a map of the process, not a schedule — timings vary by protocol and by clinic.
FORT measures follicles that responded to stimulation. FOI measures eggs actually retrieved against the starting cohort — it covers the whole pathway including retrieval.
Yes. The baseline scan does not see every follicle, so retrieval can exceed the counted antral follicles.
They answer different questions. FORT stops at follicle response; FOI covers the whole pathway through to eggs in the dish, including the retrieval itself. Read together they show where in the chain a disappointing cycle actually lost ground.
A calculator sees three or four figures. A specialist sees your history, your scans, your partner's results, and how you actually responded to treatment. If you're between cycles, changing clinics, or something in your results doesn't add up, a second opinion is the fastest way to find out whether anything would be done differently.
Free first consultation. No obligation to start treatment, and it doesn't affect your care at your current clinic.
FOI is a research-derived index used within the POSEIDON framework, not a standalone measure. Nothing here is a diagnosis or a substitute for assessment by a clinician.
A calculator gives you a number. These explain what it means, and what it does not.
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