Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Confirm whether ovulation occurs, investigate a suspected ovulatory disorder selectively, and use ovarian-reserve tests for the clinical question they can answer rather than as general fertility scores.
Ovulation assessment and ovarian-reserve assessment answer different questions. Ovulation testing asks whether an oocyte has probably been released in a particular cycle. Reserve testing estimates the remaining recruitable follicle pool and, in assisted conception, helps anticipate response to stimulation. Neither AMH nor antral follicle count directly measures oocyte competence, confirms tubal patency, evaluates sperm or predicts whether spontaneous conception will occur.
Start with cycle history: age at menarche, usual interval and variability, duration of bleeding, last menstrual period and recent changes. Regular monthly cycles make ovulation likely. Oligomenorrhoea or amenorrhoea suggests inconsistent ovulation and should prompt questions about pregnancy, PCOS features, weight change, dietary restriction, exercise, stress, galactorrhoea, thyroid symptoms, vasomotor symptoms, chronic illness and medicines that influence prolactin or the reproductive axis.
Serum progesterone rises after ovulation because the corpus luteum secretes it. During infertility investigation, collect a mid-luteal sample approximately 7 days before the expected period. The familiar day-21 test assumes a 28-day cycle; using it automatically in a 35-day cycle samples too early. With prolonged irregular cycles, test later and repeat weekly until bleeding if necessary. Interpret the result using the laboratory assay and timing, recognising that one low value may reflect mistiming rather than anovulation.
Predictable monthly bleeding without major variability makes ovulation likely, although a correctly timed mid-luteal progesterone is still offered during formal infertility investigation.
Infrequent cycles with hirsutism, acne or biochemical androgen excess suggests PCOS after pregnancy and alternative endocrine causes are addressed.
Low oestradiol with low or inappropriately normal gonadotrophins, particularly after weight loss, high exercise, stress or pituitary symptoms, indicates reduced hypothalamic-pituitary drive.
Amenorrhoea or irregular cycles with vasomotor symptoms, low oestradiol and appropriately confirmed high FSH suggests impaired ovarian function rather than simply low reserve.
A high AMH or high antral follicle count, often in PCOS, predicts stronger stimulation response and informs an OHSS-reduction strategy rather than indicating superior oocyte quality.
Progesterone peaks in the mid-luteal phase, so day 21 is appropriate only for a roughly 28-day cycle; individualise timing to expected menstruation.
NG257 specifically advises against AMH for predicting spontaneous clinical pregnancy, even though it is useful for predicting stimulation response.
AMH and AFC estimate follicle quantity and response; age remains more informative about oocyte competence and pregnancy probability.
A sample obtained before ovulation or too late in the luteal phase may be low, so dates and cycle variability matter before diagnosing anovulation.
A high AMH or AFC may predict excessive response and OHSS, making the result a safety-planning signal rather than unqualified good news.
Ordering a day-21 progesterone for every cycle length and diagnosing anovulation from a sample taken too early.
Using AMH to predict spontaneous conception, screen the general population or describe oocyte quality.
Using basal body-temperature charts as reliable confirmation of ovulation despite NICE advice against this.
Requesting prolactin and thyroid function routinely in everyone with delayed conception rather than using clinical indications.
Using FSH to predict ovarian response or assisted-conception outcome after the 2026 NG257 update.
Treating one reserve result as a verdict without age, diagnosis, assay context, ultrasound expertise or previous treatment response.
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A 29-year-old undergoing fertility investigation has regular 35-day cycles. When is serum progesterone best sampled to confirm ovulation?
National guidance is shown before implementation-dependent detail. Apply principles in context and verify current guidance when a decision affects care. Source check completed 27 Aug 2026; clinical approval remains outstanding.
Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes
If cycles are irregular, measure FSH and LH and integrate them with oestradiol, androgen features and the clinical setting. Hyperandrogenism with chronic ovulatory dysfunction supports a PCOS pathway after mimics are excluded. Low or inappropriately normal gonadotrophins with low oestradiol suggests hypothalamic-pituitary suppression, while repeatedly raised FSH with low oestradiol suggests ovarian insufficiency. Hormonal contraception and exogenous sex steroids can make these results uninterpretable.
Do not request prolactin as a universal fertility screen. It is indicated with an ovulatory disorder, galactorrhoea or known or suspected pituitary tumour. Confirm modest elevations under appropriate sampling conditions, review pregnancy, medicines, renal and thyroid disease, and distinguish macroprolactin when the laboratory advises. Thyroid function is likewise symptom led in fertility assessment; a small incidental biochemical variation should not be made the default explanation for delayed conception.
The 2026 NICE reserve recommendations correct a common misunderstanding. Age remains the initial predictor. AMH must not be used to tell someone whether spontaneous pregnancy will occur. AMH or transvaginal ultrasound antral follicle count can predict low or excessive ovarian response, help choose stimulation strategy and support counselling about assisted-conception prognosis. NICE no longer recommends FSH to predict ovarian response or assisted-conception outcome.
AMH is secreted by granulosa cells in growing pre-antral and small antral follicles. A lower result usually accompanies a smaller recruitable pool, while a high result, often seen with PCOS, can indicate a stronger response and higher OHSS risk. Assays and decision thresholds vary, and hormonal contraception, ovarian surgery and some treatments can affect interpretation. A low AMH does not prove infertility; a high AMH does not preserve age-related oocyte quality.
Antral follicle count is the number of small follicles visualised by a trained operator, usually early in the cycle. It is immediate and anatomically informative but operator and equipment dependent. Use either AMH or AFC according to expertise and the treatment question; repeated measurements rarely create certainty. Communicate results as one component of an integrated assessment including age, duration, diagnosis, semen, tubal status and previous treatment response.