Egg Quality and Ovarian Reserve Explained

Quantity vs. quality

Ovarian reserve refers to the number of remaining eggs, which declines with age. Anti-Müllerian hormone (AMH) and antral follicle count estimate quantity but do not directly measure egg quality.

Egg quality—the chromosomal health of eggs—also declines with age, especially after the mid-30s, which raises the chance of miscarriage and conditions like Down syndrome.

Supportive steps

Antioxidant-rich nutrition, vitamin D sufficiency, not smoking, healthy weight, and managing conditions like PCOS or thyroid disorders support reproductive health.

If you are planning pregnancy later, discuss egg freezing and reserve testing with a fertility specialist while options are broadest.

What ovarian reserve means

Ovarian reserve refers to the number and quality of eggs remaining, both of which decline with age—gradually through the thirties and more steeply after the late thirties. Egg quality strongly influences the chance of conception and healthy pregnancy. Tests such as AMH blood levels and antral follicle counts estimate reserve but do not guarantee or rule out conception.

Supporting egg health and planning ahead

A balanced diet, not smoking, healthy weight, and managing conditions like thyroid disorders support overall reproductive health. For those who wish to delay childbearing, egg freezing is an option that is most effective when done at a younger age. A fertility specialist can interpret tests in context and discuss realistic options.

What Ovarian Reserve Actually Means

Ovarian reserve refers to the quantity and, to some extent, the functional potential of the remaining egg-containing follicles in a woman's ovaries. At birth, the ovaries contain all the eggs a woman will ever have — approximately one to two million primordial follicles. This number falls continuously throughout life through a process called atresia (natural follicle loss), independent of whether ovulation is occurring or whether hormonal contraceptives are being used. By puberty, around 300,000–500,000 follicles remain. By the late 30s, the number and recruitment capacity decline more steeply until the menopause, when the functional reserve is essentially exhausted.

Ovarian reserve is distinct from egg quality, although the two are related. Reserve describes the pool size; quality describes the chromosomal and molecular integrity of individual eggs. A woman with a low ovarian reserve may still produce good-quality eggs; a woman with a normal reserve may have quality issues if she is older or has other risk factors. Both parameters matter for fertility and IVF outcomes, and the interplay between them is why reserve tests alone cannot predict treatment success with certainty.

Measuring Ovarian Reserve: AMH and Antral Follicle Count

Anti-Müllerian hormone (AMH) is produced by the granulosa cells of small antral and preantral follicles and is the most widely used serum marker of ovarian reserve. Unlike FSH — which must be measured on day 2–5 of the cycle — AMH is relatively stable across the cycle and can be measured at any point. A low AMH (below approximately 1.0 ng/mL, though laboratory reference ranges vary) indicates a reduced functional pool of follicles. A high AMH may indicate polycystic ovarian morphology. AMH does not measure egg quality, only the number of recruitable follicles.

The antral follicle count (AFC) is performed by transvaginal ultrasound, typically in the early follicular phase. The clinician counts small follicles (2–10 mm in diameter) across both ovaries. An AFC of 7–14 is generally considered normal; below 7 suggests diminished reserve; above 20 may indicate polycystic morphology. AFC and AMH together provide a more complete reserve picture than either alone. Both decline with age but can also be reduced by prior ovarian surgery, chemotherapy, smoking, endometriosis, and certain genetic conditions.

Egg Quality: The Role of Chromosomal Integrity

Egg quality is predominantly determined by chromosomal integrity — whether the egg carries the correct number and structure of chromosomes. Chromosomally normal eggs are called euploid; those with abnormalities are called aneuploid. Aneuploidy is the most common cause of failed fertilisation, failed implantation, and first-trimester miscarriage. The proportion of aneuploid eggs increases substantially with age: roughly 25% at age 30, rising to 50–60% by age 40, and approaching 80–90% by the mid-40s. This age-related decline is the primary driver of falling natural fertility and rising miscarriage rates as women age.

The biological mechanism involves the spindle apparatus — the structure that separates chromosomes during cell division. As eggs age within the ovary over decades, the proteins that assemble this spindle degrade. When a mature egg is ovulated, the final cell division (meiosis II) must be completed perfectly in a very short time window. If the spindle is compromised, chromosomes segregate unevenly, producing an aneuploid egg. No current treatment reverses this age-related spindle degradation, which is why egg freezing at a younger age preserves the quality present at that point in time.

Factors That Affect Egg Quality Beyond Age

While age is the dominant determinant of egg quality, several modifiable factors influence the mitochondrial energy capacity and oxidative environment of maturing follicles, and these indirectly affect egg quality. Smoking is particularly damaging — tobacco compounds are directly toxic to the granulosa cells and oocytes, and smokers reach menopause on average 1–2 years earlier than non-smokers. Excessive alcohol, high BMI, poorly controlled thyroid disease, and exposure to endocrine-disrupting chemicals (found in some plastics, pesticides, and personal-care products) have also been associated with impaired oocyte development.

Coenzyme Q10 (CoQ10) has attracted research interest because it is essential for mitochondrial ATP production — the energy source that powers chromosomal separation. Mitochondrial function in oocytes declines with age, and animal studies have shown CoQ10 supplementation can partially restore it. Human data is more limited but encouraging. DHEA (dehydroepiandrosterone) supplementation has been used in some fertility centres for women with diminished ovarian reserve, showing modest improvements in AMH and IVF cycle outcomes in some trials, though it is not universally recommended and should only be used under clinical supervision.

Endometriosis deserves specific mention. Endometriotic tissue produces reactive oxygen species that create an oxidative environment in the follicular fluid surrounding developing eggs. Women with endometriosis — particularly those who have had ovarian endometrioma surgery — often have both lower AMH and reduced egg quality compared to age-matched controls. Management of endometriosis in the context of fertility planning requires careful coordination between endometriosis specialists and reproductive medicine teams.

What Diminished Ovarian Reserve Means for Fertility Treatment

Diminished ovarian reserve (DOR) does not mean conception is impossible — it means the window of opportunity may be narrower and the response to fertility medications may be reduced. In IVF, women with DOR typically produce fewer eggs at egg collection despite higher doses of stimulation medication. Fewer eggs mean fewer opportunities for fertilisation, fewer embryos to assess, and therefore a reduced chance of having euploid embryos available for transfer. This is why time becomes a critical variable once DOR is identified.

Women with DOR planning IVF may benefit from personalised stimulation protocols — such as antagonist protocols with maximal follicle-stimulating hormone dosing, luteal phase stimulation for a second retrieval in the same month, or the use of clomiphene or letrozole alongside gonadotrophins in poor responders. Pre-implantation genetic testing for aneuploidy (PGT-A) can identify chromosomally normal embryos from a limited cohort, improving the probability that each embryo transferred has a realistic chance of implantation.

Egg Freezing and Ovarian Reserve: Making Informed Decisions

Elective egg freezing (social freezing) has become more accessible as vitrification — rapid ultra-cooling — improved survival rates of frozen-thawed eggs to above 90% in most modern laboratories. Women considering egg freezing should understand that outcomes are strongly influenced by the age at freezing and the number of mature eggs stored. Clinicians often use the guideline that banking 15–20 mature eggs before age 35 provides a reasonable chance of at least one live birth if the eggs are used, though individual outcomes vary.

AMH testing and AFC before deciding to freeze helps calibrate expectations. A woman with a low AMH at 32 may benefit from freezing sooner than planned; a woman with a high AFC at 36 may retrieve more eggs per cycle than the average. These numbers inform — they do not determine — the decision. Egg freezing is not a guaranteed future pregnancy; it is a preservation of the fertility potential present at the time of freezing. This nuance is important for informed consent.

Common Misconceptions About Ovarian Reserve Tests

Misconception: 'A normal AMH means I have no fertility problems.' AMH reflects follicle quantity, not egg quality, not tubal patency, not uterine receptivity, and not sperm quality. A woman with a normal AMH can still have difficulty conceiving due to any of these other factors. Conversely, a low AMH does not guarantee infertility — it indicates reduced time to act, not impossibility.

Misconception: 'If my AMH is low, I should start IVF immediately.' Not necessarily. For a 28-year-old with a low AMH who has been trying for only two months, immediate IVF is unlikely to be the right first step. The AMH result should be placed in the context of age, cycle regularity, reproductive history, and partner fertility. The urgency of response to a low AMH is much greater at 38 than at 28.

Frequently Asked Questions

Q: Can I improve my ovarian reserve? A: The total pool of follicles cannot be increased — lost follicles do not regenerate. However, optimising the microenvironment in which remaining follicles develop — through quitting smoking, achieving a healthy weight, managing thyroid disease, reducing oxidative stress through diet and supplementation — can support the best possible development of the eggs that remain. This is not the same as increasing reserve, but it is genuinely meaningful.

Q: Does being on the contraceptive pill affect my ovarian reserve? A: The pill suppresses follicle recruitment while you take it, temporarily lowering AMH readings. This is a reversible suppression — reserve returns to its natural level within weeks of stopping. Women coming off the pill for fertility testing should ideally wait at least one to three months for AMH levels to reflect true reserve. AMH measured while on the pill may underestimate the true reserve.

Q: Should I test my ovarian reserve in my late 20s even if I am not planning pregnancy yet? A: Routine reserve testing in young women without fertility concerns is not currently recommended as standard screening. However, if you have risk factors — a family history of early menopause, prior ovarian surgery, chemotherapy, or irregular cycles — early testing is reasonable and informative. For women interested in knowing their reserve as part of reproductive life planning, it is a legitimate personal choice, provided the results are interpreted in proper context by a clinician.

Q: If I have one ovary, is my reserve halved? A: Not necessarily halved in terms of fertility impact. The remaining ovary often compensates by recruiting more follicles, and many women with a single ovary have only modestly reduced fertility compared to two-ovary controls. However, AMH and AFC will be lower than if both ovaries were present, and if the remaining ovary was itself affected by the condition requiring surgery, reserve may be more substantially reduced. Follow-up assessment with a reproductive specialist is advised.