Back in 1947, a French physiologist named Alfred Jost was running experiments that sounded, frankly, a little odd. He was surgically removing the budding gonads from rabbit embryos while they were still inside the womb, at the earliest stage of development. What he found was striking: take away the gonads entirely, and any embryo — regardless of genetic sex — develops along female lines, growing fallopian tubes, a uterus, the upper vagina. Leave the testes in place, though, and those same female structures, known as the Müllerian ducts, simply disappear. Jost concluded that testes must be releasing something beyond testosterone — something whose entire job was to make those female ducts regress. By 1953, he'd given that mystery substance a name: Müllerian-inhibiting factor.
Decades later, that same substance got renamed anti-Müllerian hormone, or AMH. And it turned out to play a completely different role in adult women: it's produced by cells lining growing ovarian follicles, and its level in the bloodstream turned out to be one of the best available clues to how many eggs a woman has left. A hormone first discovered for making female structures vanish in male embryos ended up becoming the single most useful marker of female fertility — reproductive science does love an odd plot twist.
Ovarian reserve is simply the number of eggs currently available to a woman's ovaries. Men keep producing sperm continuously; women don't get that luxury. You're born with a fixed stock of primordial follicles — somewhere around one to two million at birth — and that number only ever goes down, never up. By the time your first period arrives, you're down to roughly 300,000 to 400,000. By menopause, just a few hundred remain. Most of those follicles never even make it to ovulation; the overwhelming majority quietly disappear at various stages along the way.
Two main tools are used to assess ovarian reserve today: counting antral follicles on ultrasound (AFC) and a blood test for AMH. Both only became routine clinical practice fairly recently — around the late 1990s and early 2000s, once fertility specialists started looking systematically for a way to predict how a woman's ovaries would respond to stimulation before IVF.
Antral follicles are the small, ultrasound-visible sacs, 2 to 10 mm across, present in the ovaries at the start of every cycle. As we covered in the article on the dominant follicle, exactly one of them eventually pulls ahead of the pack. But for reserve testing, what matters isn't who wins — it's how many runners showed up to the starting line in the first place.
The count is done via transvaginal ultrasound, usually on day 2 to 5 of the cycle, when the ovaries are at their quietest and the follicles are easiest to tell apart. The sonographer scans both ovaries in turn and adds up every visible follicle of the right size. It's a slightly subjective method — results can shift a bit depending on the operator's experience and the equipment — but it remains one of the most accurate and accessible ways to estimate reserve, and it's both cheaper and faster than a blood draw.
| Antral follicle count (AFC) | How it's read | What it means in practice |
|---|---|---|
| 0–3 | Very low reserve | Weak response to stimulation expected; donor programs often come up |
| 4–7 | Diminished reserve | IVF is still possible, but the protocol is tailored individually |
| 8–15 | Normal reserve | Typical, expected response across most protocols |
| 16–20 | High reserve | Good outlook, but higher risk of ovarian hyperstimulation (OHSS) |
| Over 20 | Very high reserve | Often comes with PCOS; needs a more careful protocol |
These numbers are a guide, not a diagnosis. If your AFC reads 6 in one cycle and 9 in the next, that's not a contradiction — the count naturally fluctuates somewhat from cycle to cycle, and any result should be read alongside age, symptoms, and the bigger clinical picture.
AMH is produced by granulosa cells, the lining that surrounds a growing follicle from its earliest stages right up until it reaches 4 to 6 mm. That means blood AMH levels give a fairly direct readout of how big the standing reserve of follicles is — the pool that's poised to start growing over the coming months.
The hormone itself was first detected in human follicular fluid in 1993, and by 2002 it had been turned into a routine serum blood test that any lab could run. Since then, AMH testing has become one of the most requested assays in reproductive medicine. In the UK, people commonly just call it the "egg count test," even though, technically, it doesn't count eggs directly — it estimates their number through an indirect hormonal trace.
AMH has one practical edge over ultrasound: its level barely shifts across the cycle, so blood can be drawn on any day at all, with no need to time it to a particular phase. That's convenient both for the patient and for the clinic running the test.
Plenty of studies have compared the two methods head to head, and they generally land in the same place: the two measurements correlate well with each other and do a reasonably good job predicting how many eggs a stimulated IVF cycle will yield. A handful of studies have found antral follicle count to be slightly more accurate at predicting the actual egg count, though the gap is small, and in practice most doctors run both tests together rather than picking one over the other.
One important caveat applies to both: neither AMH nor AFC measures egg quality — only quantity. A high reserve doesn't guarantee genetically healthy eggs, and a low reserve doesn't mean the remaining eggs are worse quality. Quality is driven primarily by age, not by how large the remaining stock happens to be.
A low AMH or a small AFC is not a diagnosis of infertility, and it's not a reason to give up. These tests predict how the ovaries will respond to hormonal stimulation in an IVF protocol — they're much weaker predictors of whether natural conception will happen. A woman with a modest reserve can absolutely conceive naturally, provided ovulation is regular and that single egg each cycle happens to be a good one. The reverse holds too: a perfectly normal reserve doesn't rule out other causes of infertility, from blocked tubes to a male-factor issue.
That's why reserve test results are best discussed with a doctor as part of the full clinical picture, rather than read in isolation as some kind of final verdict.
For MAPASGEN users, reserve testing matters in a handful of recurring situations. For women weighing egg freezing for the future, an AMH result helps gauge how many retrieval cycles it might take to bank a reasonable number of eggs. For anyone choosing an egg donor, it's worth knowing that reputable donor programs always check the donor's own reserve as a standard part of medical screening. And for couples or single parents preparing for IVF, the test result shapes which stimulation protocol the doctor recommends and what a realistic egg yield looks like for a single cycle.
The road from Alfred Jost's rabbit-embryo experiments in the 1940s to a routine blood test now available at any private lab took a little over fifty years. It's a good reminder of how oddly science sometimes moves: a fundamental discovery in one corner of embryology can resurface decades later as a practical tool in a completely different field.
A reserve test is a medical procedure, not a legal one, so unlike egg donation or surrogacy, it isn't governed by dedicated legislation in almost any country. Still, what it's called, who typically pays for it, and how built-in it is to a standard patient pathway varies quite a bit from place to place.
| Country | What it's called and who typically pays | Notable detail |
|---|---|---|
| United Kingdom | "Egg count test" — usually out of pocket, £50–300 | Mail-in home test kits are widely popular |
| Germany | "Eizellreserve-Test" — typically not covered by basic insurance | Usually ordered alongside IVF preparation |
| France | Free as part of a fertility specialist consultation before IVF | Built into the standard work-up before a state-funded cycle |
| Spain | Around €100, usually part of a paid fertility check-up | Heavily advertised by private clinics as a first step |
| Portugal | Has been studied as part of a national screening programme | Health-economics research has modelled savings from early detection |
| Denmark | Standard part of work-up before donor and stimulated cycles | Strong culture of seeing a fertility specialist early |
| Czech Republic | Available privately, at lower prices than Western Europe | Often done for foreign patients ahead of donor-egg cycles |
| Israel | Covered by state insurance as part of an infertility work-up | One of the highest rates of fertility check-ups in the world |
| Brazil | Mostly paid for privately, at private labs | Demand is rising alongside delayed childbearing trends |
| Greece | Paid for, usually bundled with a specialist appointment | Often offered to foreign patients packaged with a scan |
| Cyprus | Paid for, usually bundled with a specialist appointment | A popular destination for combining a test with a holiday |
| Ukraine | Paid for, among the most affordable prices in Europe | Often included in a standard pre-cycle work-up package |
In the UK, the test has firmly entered everyday vocabulary as the "egg count test," and mail-in home kits have long been a familiar product on the market. In France and Israel, it's typically folded into the standard work-up ahead of a state-funded IVF cycle, so patients rarely pay for it separately. In the Czech Republic and Ukraine, it remains a paid test but noticeably cheaper than in Western Europe, which partly explains why patients travel there for pre-screening ahead of donor-egg programs. In Portugal, reserve testing has even been the subject of national health-economics modelling, with researchers studying whether early, widespread detection of diminished reserve could shorten the diagnostic journey and save the system money further down the line on more expensive treatment.
At the end of the day, AMH and AFC aren't a verdict and they aren't a guarantee — they're just two numbers that let you glimpse the current state of your ovaries a little before it would otherwise reveal itself. The earlier a woman learns these numbers — whether out of curiosity at 25 or ahead of a specialist visit at 38 — the more room she has to make a calm, considered decision: wait, freeze eggs, start treatment, or look into a donor programme. A reserve test is best treated not as a cause for alarm, but as just another routine piece of information about your own body, on par with a haemoglobin check or a blood-pressure reading.