Antral Follicle Count (AFC) — Definition, Normal Range & Fertility Impact

Antral follicle count (AFC) is the number of small resting follicles (2–10mm) visible in both ovaries on a Day 2–4 transvaginal ultrasound scan. Each antral follicle contains a sleeping egg — so AFC is a direct measure of remaining egg supply (ovarian reserve). Normal AFC is 10–20 total. AFC is counted at every baseline fertility scan and directly determines the starting dose of IVF stimulation injections.

AFC ranges for IVF response prediction: <5 total = poor responder (expect 1–4 eggs retrieved; high-dose protocol; consider poor responder strategies); 5–10 = low-normal (6–10 eggs expected); 10–20 = normal/good (10–15 eggs expected; standard protocol); >20 = high responder/PCOS pattern (15–25+ eggs possible; low-dose protocol essential; OHSS risk). No AFC is "too low" to try IVF — even AFC 1–2 can result in a successful cycle if the single egg fertilises and develops to blastocyst.

AFC cannot be permanently increased — the primordial follicle pool is fixed at birth and declines irreversibly with age. However, AFC measurement varies slightly between cycles (±2–3 follicles) and can appear artificially low if a baseline cyst is present (obscuring small follicles) or if the TVS is performed at mid-cycle (fewer antral follicles visible). DHEA supplementation (75mg/day for 3+ months) has some evidence for modest AFC improvement in poor responders, though data is mixed. The most reliable way to "improve" AFC outcomes is to optimise IVF stimulation protocol based on the actual AFC count.

AFC and AMH both measure ovarian reserve but from different perspectives: AFC = structural (ultrasound count of visible antral follicles on Day 2–4 TVS); AMH = biochemical (blood test measuring hormone produced by all small follicles, any day of cycle). They correlate well (~0.7 correlation). AFC is operator-dependent (requires TVS expertise); AMH is laboratory-based and more standardised. Discordant results: low AMH + high AFC → trust AFC; high AMH + low AFC → likely PCOS with large follicles obscuring count. Best practice: use both together for maximum accuracy.

AFC predicts IVF response (egg yield) but is a weaker predictor of live birth rate than egg yield alone suggests, because egg quality also matters. A woman with AFC 3 who retrieves 2 eggs and gets 1 blastocyst has a 40–50% chance of live birth from that transfer — the same as a woman with AFC 15 who retrieves 12 eggs and gets 1 blastocyst. The difference is cumulative chances: a higher AFC gives more embryos to freeze, allowing multiple transfer attempts. Live birth rates per egg retrieved are similar regardless of AFC — it is the total number of attempts that differs.