What is Ovarian Reserve?
Ovarian reserve is the number of immature eggs (oocytes) remaining in your ovaries at any given time. You are born with all the eggs you will ever have — around 1-2 million at birth, falling to about 300,000 at puberty and continuing to decline throughout your reproductive years. Of these, only around 400-500 will ever ovulate. Reserve declines naturally with age, but the rate varies between women due to genetics, lifestyle and medical factors. Testing ovarian reserve helps estimate where you are on this curve, but importantly does not directly measure egg quality — which is the bigger driver of fertility outcomes after age 35.
The Three Main Reserve Tests
AMH (anti-Müllerian hormone): Blood test that can be done any day of the cycle. Reflects the pool of small follicles. Stable and reproducible. Most widely used test today.
Antral follicle count (AFC): Transvaginal ultrasound counting the small (2-9mm) follicles visible on day 2-5 of cycle. Direct visual measurement, but operator-dependent.
Day 3 FSH and oestradiol: Older test. Elevated FSH indicates the brain is working harder to stimulate the ovaries — a sign of declining reserve. Less precise than AMH or AFC.
Interpreting AMH Results
High AMH (>3.5 ng/mL or >25 pmol/L): Often seen in PCOS. Strong response to stimulation but risk of OHSS
Normal AMH (1.0-3.5 ng/mL or 7-25 pmol/L): Average ovarian reserve for age
Low AMH (0.5-1.0 ng/mL or 3.5-7 pmol/L): Reduced reserve. May respond less well to stimulation but pregnancy still very possible
Very low AMH (<0.5 ng/mL or <3.5 pmol/L): Diminished ovarian reserve. Time may be limited and IVF may be less effective
Important: AMH must be interpreted by age. A "low" AMH at 28 is much more concerning than the same value at 42
What These Tests Cannot Tell You
Ovarian reserve tests measure egg quantity, not quality. A 40-year-old with high AMH still has 40-year-old eggs with the same chromosomal risk as her peers. AMH is not a reliable predictor of natural conception chances — many women with low AMH conceive naturally, and many with high AMH struggle. AMH cannot diagnose infertility on its own. Tests are most useful for predicting IVF response, planning timing of treatment, identifying women who might benefit from earlier intervention, and informing decisions about fertility preservation. Always interpret results with a fertility specialist who considers your full clinical picture.