First principle: two distinct questions
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- Ovulation = is an oocyte released this cycle? Regular 21–35‑day cycles usually mean yes — often no test needed; confirm with mid‑luteal progesterone (timed to her cycle) if unclear.
- Ovarian reserve = how many oocytes remain and how will she respond to stimulation? Assessed by AMH (any cycle day), antral follicle count, and early‑follicular FSH/estradiol.
The overriding variable
Two dissociations that matter
- Ovulating ≠ good reserve (a woman can ovulate monthly with low reserve).
- Low reserve ≠ sterile — reserve tests predict response to stimulation, not the possibility of natural conception; they should not be used as general screening or to extinguish hope. 🚩
PCOS re‑examined
Many follicles, failed selection, anovulation → treat by inducing ovulation (letrozole first, Concept 18). "Many follicles" is not "good ovulation."
Modern corrections
- Abandon fixed "day‑3 FSH cut‑off = fertility verdict"; interpret with age + AMH + AFC + assay.
- The clomiphene challenge test and inhibin B are not recommended for routine reserve testing.
Pitfalls
- Conflating ovulation with reserve; using a low AMH to declare sterility.
- Rigid "day‑21" progesterone in non‑28‑day cycles (Concept 13).
Pearls
- 🎯 Regular cycles ≈ ovulatory. Reserve = AMH + AFC + early FSH. Age beats all.
- 🩺 Reserve tests forecast stimulation response, not destiny — counsel accordingly.
Next → Even with egg and sperm, the tube must work (Concept 32).