Age and Fertility — what changes, when, and what to do about it.

How age affects fertility

Two parallel declines happen with age. Quantity — the number of remaining eggs in the ovaries — falls steadily from teenage years. Quality — the chromosomal normality of those eggs — declines more dramatically from the late 30s onward, driving the rise in miscarriage and aneuploidy with age.

Age-related infertility isn't really one condition. It's the cumulative effect of these two declines. The result: longer time to natural conception, higher miscarriage rate, lower per-cycle IVF success.

The egg quality vs quantity distinction

Quantity (AMH, AFC)

Predictable, age-dependent decline. The pool of remaining eggs gets smaller every year. AMH and antral follicle count quantify this. A 40-year-old with average reserve has fewer eggs than a 28-year-old with average reserve — mathematically, biologically, definitively.

Quality (aneuploidy rate)

The percentage of eggs that are chromosomally abnormal rises with age. At 25, roughly 20% of eggs are aneuploid; at 35, around 35%; at 40, 60–70%; at 45, 85%+. This is why miscarriage and birth-defect rates rise — not because of "old eggs" in a folksy sense, but because of measurable, increasing chromosomal errors during egg meiosis.

Quality is what most limits older-age IVF success. IVF can retrieve eggs you have; it can't make them genetically normal.

Male age matters too

Female age effects dominate the fertility conversation, but male age is real:

• Sperm DNA fragmentation increases gradually with age, more visibly after 45.
• Spontaneous mutation rate in sperm rises modestly with paternal age.
• Conditions like autism, schizophrenia, and certain genetic disorders have weak but real associations with advanced paternal age.

Male age doesn't carry the same fertility cliff that female age does, but it isn't irrelevant.

What changes at each age band

Under 35

Fertility is generally good. Most couples conceive within 6–12 cycles of trying. When trouble arises, the workup tends to find specific causes (PCOS, mild male factor, endometriosis, tubal factor) rather than age itself being the issue. Expectant management for 12 months of trying is reasonable before active workup.

35 to 37

Fertility starts noticeably declining. Per-cycle natural conception drops to 12–15%. Miscarriage rate rises to 20% from a baseline of 12–15%. The recommendation: don't wait 12 months — start active workup after 6 months of trying.

38 to 40

The decline accelerates. Per-cycle natural conception ~7–10%. Miscarriage ~30%. IVF live-birth rates per cycle: 20–25%. The recommendation: see a fertility specialist after a few months of trying, not after a year.

41 to 42

Per-cycle natural conception ~3–5%. Miscarriage 40%+. IVF success drops to 10–15% per cycle with own eggs. Active treatment from the start makes sense. PGT-A is worth considering. Donor egg discussion enters the conversation.

Over 42

Own-egg IVF success drops below 5% per cycle. Donor egg IVF becomes the more efficient path for many. We have honest conversations about realistic expectations — pregnancy is still possible with own eggs, but the path is long and the math is challenging.

Treatment strategies by age band

Under 35

Standard stepwise care — lifestyle, evaluation, ovulation induction if needed, IUI, then IVF. Time is on your side.

35 to 37

Compressed stepwise care — complete workup quickly, move through OI/IUI cycles in 3–4 months, move to IVF after that. Don't drift.

38 to 40

Often skip IUI in favour of IVF. PGT-A becomes a reasonable consideration. Maximise eggs per cycle. Fewer IUI attempts before moving on.

41 to 42

IVF with PGT-A is the typical first-line approach. Donor egg discussion happens earlier so it doesn't feel like a last-resort surprise later.

Over 42

Own-egg IVF if desired and AMH supports it, but with realistic expectations. Donor eggs offer 50–60% per-transfer success regardless of recipient age — the math often favours moving sooner.

Fertility preservation as prevention

For women not ready to conceive but knowing they'll want a family later, egg freezing in the late 20s to early 30s preserves better biology than waiting to try at 38 and finding out reserve has declined. The conversation about preservation is best had before you need to think about treatment — not after.

The honest truth about age

IVF doesn't reverse age. Marketing sometimes implies it can; the data say otherwise. What IVF and modern fertility care do is:

• Optimise per-cycle chances with the eggs you have.
• Use PGT-A to select chromosomally normal embryos.
• Identify and address other contributing factors (uterine, hormonal, male).
• Offer donor eggs as an effective alternative when own-egg cycles aren't working.
• Preserve current biology through egg/embryo freezing when timing isn't right yet.

None of these reverses the underlying biological clock. Treatment is most useful when matched honestly to age and reserve, not when over-promised.

How I work with age-related infertility

1. Realistic projections from day one. No false reassurance, no doom-mongering — just the actual math for your age and reserve.
2. Speed matches age. Younger patients can take time; older patients shouldn't.
3. Donor egg conversations happen early. Not as a recommendation, but as a known option so it doesn't feel like a last-minute decision.
4. Preservation when appropriate. If you're 32 and not ready to try yet, we discuss freezing as an option — not a sales pitch, just information.