AMH, AFC and 'ovarian reserve': what the numbers predict — and what they don't

Before IVF, your doctor will look at two measures of ovarian reserve — a rough estimate of how many eggs remain in the ovaries and how they might respond to stimulation.

The two tests

AMH (anti-Müllerian hormone) is a blood test. It's made by the small follicles waiting in the ovary, so higher AMH usually means more follicles that could grow. It's fairly stable across the cycle. Values are given in ng/ml or pmol/l (1 ng/ml ≈ 7.14 pmol/l). Very roughly:

AMH (ng/ml)	Often described as
under 0.5	very low reserve
0.5 – 1.2	low
1.2 – 3.5	typical for age 30–38
over 3.5	high (often seen with PCOS)

Labs and clinics use slightly different cut-offs; treat these as bands, not lines. Embryology labs sometimes group patients by AMH band when they look at their own results, because it separates patient factors from lab factors.

AFC (antral follicle count) is a transvaginal ultrasound early in the cycle counting the small follicles (2–10 mm) on both ovaries. It measures the same thing directly. AMH and AFC usually agree; when they don't, the doctor weighs both.

What they predict well

• How many eggs a stimulation is likely to produce. This is the main use, and it's good.
• How to dose the drugs. Low reserve → higher dose or different protocol; high reserve → gentler dose to avoid over-response.
• Whether egg freezing or a second cycle is worth planning sooner rather than later.

What they predict poorly

• Egg quality, which is what determines whether an embryo can become a baby. Quality tracks mostly with age, not with AMH. A 32-year-old with low AMH usually has fewer but good eggs; a 42-year-old with high AMH usually has more eggs of which fewer are chromosomally normal.
• Your chance of pregnancy per embryo. Once a good blastocyst exists, AMH has told its story.
• Natural fertility. Low AMH does not mean you can't conceive without help; it means the reserve is smaller.

How embryologists use it

In the lab, AMH mostly matters as context. If a cycle yields fewer eggs than expected for that AMH, the trigger timing or stimulation is examined; if fewer of the eggs than usual are mature or fertilise, the question is different. Good labs look at their fertilisation and blastocyst rates within AMH bands, so that a run of low-reserve patients doesn't look like a lab problem and a lab problem doesn't hide behind patient mix.