For years, the standard way to define "poor responder" in IVF was the Bologna criteria (2011). It grouped everyone with low reserve, prior poor response, or advanced age into one big bucket. That was a problem — a 28-year-old with low AMH is clinically very different from a 42-year-old with normal AMH, but both were "poor responders."
The POSEIDON group (Patient-Oriented Strategies Encompassing IndividualizeD Oocyte Number) proposed a new framework in 2016 that splits patients into four distinct groups. It's now the standard way experienced REIs think about diminished-response IVF.
The Four Groups
| Group | Age | Ovarian reserve | Prior response |
|---|---|---|---|
| POSEIDON 1 | <35 | Adequate (AMH ≥1.2, AFC ≥5) | Unexpectedly poor (<4 eggs or <9 eggs) |
| POSEIDON 2 | ≥35 | Adequate (AMH ≥1.2, AFC ≥5) | Unexpectedly poor (<4 eggs or <9 eggs) |
| POSEIDON 3 | <35 | Low (AMH <1.2, AFC <5) | N/A (predicted poor) |
| POSEIDON 4 | ≥35 | Low (AMH <1.2, AFC <5) | N/A (predicted poor) |
Why the Split Matters
Each group has a different biological story and a different treatment strategy:
POSEIDON 1: Young, normal reserve, poor response
Something is off in the response mechanism — receptor sensitivity, LH activity, oocyte competence. Egg quality is usually good because of age; the problem is quantity.
Strategy: change protocol. Try antagonist, higher gonadotropin dose, add LH activity, consider dual stimulation (DuoStim). Genetic screening for FSH receptor polymorphisms occasionally illuminating.
POSEIDON 2: Older, normal reserve, poor response
Age is starting to affect response despite adequate reserve. Egg quality is a bigger concern here than in group 1.
Strategy: similar protocol adjustments plus more aggressive consideration of PGT-A testing and multiple retrievals to bank enough euploid embryos.
POSEIDON 3: Young, low reserve
Quantity is the issue but egg quality remains age-appropriate. High potential per egg, low number of eggs.
Strategy: maximize egg quality with priming (estrogen or testosterone), CoQ10, DHEA, mild-stim protocols, multiple retrievals. Egg banking is often the framing.
POSEIDON 4: Older, low reserve
Both quantity and quality challenges. The hardest group. Live birth rates per own-egg cycle are meaningfully lower.
Strategy: honest counseling. Multiple retrievals may still produce euploid embryos. Donor egg conversation should happen early and openly rather than after multiple failed cycles.
You can't fix your ovarian age. Every credible treatment strategy for POSEIDON 2 and 4 patients acknowledges this. Anyone selling you “ovarian rejuvenation” that will reverse your reserve or quality should be viewed skeptically. Real strategies focus on maximizing what you have, not fabricating what you don't.
What the Framework Changes in Practice
Target oocyte number
POSEIDON proposed treatment targets — how many eggs are actually needed for a reasonable live-birth chance, given age and quality expectations. This shifts the conversation from "get as many eggs as possible" to "get enough good eggs for at least one euploid embryo," which changes protocol intensity choices.
Multiple retrievals as strategy
For POSEIDON 3 and 4 (low reserve), single retrievals are often insufficient. Multi-cycle strategy with embryo banking becomes standard rather than a disappointment reaction.
Donor egg conversation timing
For POSEIDON 4 patients, mainstream fertility programs increasingly discuss donor egg IVF at first consultation rather than after 2–3 failed own-egg cycles. Faster path to live birth, often better economics overall.
Applying This to Your Situation
Ask your clinic which POSEIDON group they've classified you into. If they haven't used the framework at all, that's not necessarily a red flag — plenty of experienced REIs use their own mental categories. But a clinic that can't explain the framework isn't at the current standard of care.
The most valuable question you can ask: "Given my group, what oocyte target are we aiming for, and how many retrievals do you realistically expect will get us there?"
Colombia-Specific Considerations
Colombian fertility centers with international patient programs generally use POSEIDON classification. Multi-cycle packages are more affordable than US equivalents, which materially changes what's feasible for POSEIDON 3 and 4 patients — the option of 2–4 retrievals is realistic where it might be economically prohibitive in the US.
Trying to understand where you stand?
Send us your recent AMH, FSH, AFC, age, and prior cycle summaries. We'll help you interpret your POSEIDON classification and understand realistic options.
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