Understanding female fertility
Ovarian reserve: what it is and is not
Ovarian reserve means the number of eggs remaining. It is estimated by AMH or antral follicle count.
ESHRE (2026) makes two separate strong recommendations that are worth holding side by side:
For predicting ovarian response — AFC or AMH is recommended.
For predicting pregnancy and live birth — AMH, AFC, basal FSH, basal LH, basal oestradiol, basal progesterone and inhibin B are not recommended. Female age and BMI are the predictors.
So reserve testing tells you how you would respond to stimulation. It does not tell you whether you will have a baby, and it is routinely presented as though it does.
A low AMH with regular cycles is not a reason to panic. Women with low AMH conceive naturally.
Egg quality versus quantity
Reserve testing counts. It does not assess quality — and quality, meaning the proportion of eggs that are chromosomally normal, tracks with age rather than with AMH.
This is why a 42-year-old with excellent AMH and a 32-year-old with low AMH face different situations despite the numbers suggesting otherwise.
The cycle
Normal menstrual frequency is 24 to 38 days under FIGO terminology — this replaced the older 21 to 35 day definition still widely quoted. Cycles are regular if the gap between shortest and longest stays within about 7 to 9 days.
Ovulation occurs roughly 12 to 16 days before your next period. The fertile window is the five days before ovulation plus the day itself — because sperm survive up to five days while the egg survives 12 to 24 hours.
That is why the days before ovulation matter more than the day after.
What can go wrong
Ovulation problems — PCOS (renamed PMOS in 2026), thyroid disorders, raised prolactin, premature ovarian insufficiency, functional hypothalamic amenorrhoea.
Tubal factors — usually from previous infection, surgery or endometriosis. Frequently symptomless.
Uterine factors — polyps, fibroids affecting the cavity, adhesions, septum.
Endometriosis — where the average diagnostic delay is measured in years.
Age-related decline in egg quality.
Several of these produce no symptoms at all. Feeling well is not evidence that nothing is wrong.
Assessment
Day 2 or 3 FSH and LH, AMH, prolactin and thyroid function. Pelvic ultrasound with antral follicle count. Tubal patency testing where indicated.
Timing in the cycle matters for several of these — a common reason results come back falsely normal.
And the male partner
Male factor is involved in a substantial proportion of cases and typically causes no symptoms. A semen analysis should be arranged at the same time, not after.
Frequently Asked Questions
What is a normal AMH level for fertility?▾
Normal AMH for fertility is 1.0–3.5 ng/mL. Values below 1.0 ng/mL suggest diminished ovarian reserve. Values above 3.5 ng/mL may indicate PCOS. AMH can be tested on any day of the cycle.
At what age does female fertility decline most rapidly?▾
Female fertility declines gradually from the late 20s, more noticeably from age 35, and significantly after age 37–38. By age 40, monthly conception rates fall below 5% per cycle due to egg quality decline. ASRM recommends seeking evaluation after 6 months of trying at age 35–40.
Can you get pregnant with low ovarian reserve?▾
Yes — low ovarian reserve reduces the number of eggs available but does not make conception impossible. Many women with low AMH conceive naturally or with IVF. IVF outcome depends more on egg quality (which correlates with age) than on quantity alone.
How do I know if I am ovulating?▾
Signs of ovulation include mid-cycle cervical mucus changes (clear, stretchy, egg-white consistency), a slight rise in basal body temperature, and a positive LH test. A blood progesterone test on day 21 of a 28-day cycle (>3 ng/mL) confirms ovulation occurred.