Is 35 actually a cliff?

No. ASRM describes the decline as gradual until the early 30s and accelerating quickly after the mid-30s — a steepening curve, not a step. Thirty-five appears everywhere because it is where the rate of change picks up, and it is the point at which the evaluation threshold shortens from a year to six months.

We conceived easily but had a miscarriage. Does that make sense with age?

It does, and it is a common and confusing pattern. Conceiving depends largely on the number of eggs; carrying depends more on quality, and quality declines faster. ASRM notes miscarriage and chromosomal abnormalities are more common in older mothers. It is not something you did.

Does my partner's age matter?

Later than yours, but yes. ASRM says the decrease in male fertility occurs later in life, with changes in sperm appearing in the mid-to-late 40s. In a couple where both are in their forties it is not only her question, and assuming otherwise can delay the right test.

I'm 38 and we've been trying four months. Should we wait?

The threshold over thirty-five is six months rather than a year, so you are close. There is no harm in booking now and asking what an evaluation would involve — appointments take time to come through, and being early costs nothing.

Before it starts · 4 min read

Age, and what it actually changes

This is the anxiety underneath most of the others, and it is usually carried in a vaguer and more frightening form than the facts warrant.

The facts are not all reassuring. They are more specific than the fear, which is generally an improvement.

Last updated August 20, 2026

The shape of the decline

ASRM's description is worth having exactly: the number and quality of eggs decrease naturally and progressively from birth until menopause, and the decline is gradual until the early 30s but accelerates quickly after the mid-30s.

So it is a curve that steepens, not a cliff at a particular birthday. Nothing changes overnight at thirty-five — but the rate of change is genuinely different on either side of the mid-thirties, which is why so much guidance uses that number.

Two things are falling at once. The number of eggs remaining, and their quality. Most conversations only track the first, which is also the only one a test like AMH can measure.

Why quality is the part that matters more

ASRM: it is not only more difficult to conceive — miscarriage and chromosomal abnormalities in the child are more common in older mothers.

That is the mechanism behind something people find hard to square: conceiving without difficulty and then having a loss. The two are not contradictory. Getting pregnant is largely about number; carrying is more about quality, and quality is the one that declines faster.

It also connects back to loss. Genetic abnormalities account for the majority of first-trimester losses, and their likelihood rises with age. If you have had a loss in your late thirties, that is very probably what happened, and it remains not something you caused.

The bit about him

This gets left out of nearly every conversation about age and fertility, and it should not be.

ASRM: a decrease in a man's fertility appears to occur later in life than in a woman's, and in their mid-to-late 40s men experience changes in their sperm that can cause issues with fertility.

Later is not never. In a couple where both partners are in their forties, treating age as exclusively her issue is both inaccurate and unkind, and it can slow the investigation down in exactly the way the male-factor page describes.

What to actually do about it

Use the shorter clock. ASRM: under thirty-five, ask for an evaluation after a year of trying; over thirty-five, after six months. Those are not arbitrary — the six-month version exists precisely because waiting costs more when the curve is steeper.

If you are over forty, the reasonable move is to raise it at the start rather than working through a waiting period.

And do not use a test result to override the clock in either direction. A reassuring AMH is not a reason to keep waiting past the threshold, and an unnerving one does not mean it will not happen — that page covers why.

The thing that is genuinely in your control is the timing of the ASK, not the biology. That is a smaller lever than anyone wants and it is a real one.

Common questions

Is 35 actually a cliff?: No. ASRM describes the decline as gradual until the early 30s and accelerating quickly after the mid-30s — a steepening curve, not a step. Thirty-five appears everywhere because it is where the rate of change picks up, and it is the point at which the evaluation threshold shortens from a year to six months.
We conceived easily but had a miscarriage. Does that make sense with age?: It does, and it is a common and confusing pattern. Conceiving depends largely on the number of eggs; carrying depends more on quality, and quality declines faster. ASRM notes miscarriage and chromosomal abnormalities are more common in older mothers. It is not something you did.
Does my partner's age matter?: Later than yours, but yes. ASRM says the decrease in male fertility occurs later in life, with changes in sperm appearing in the mid-to-late 40s. In a couple where both are in their forties it is not only her question, and assuming otherwise can delay the right test.
I'm 38 and we've been trying four months. Should we wait?: The threshold over thirty-five is six months rather than a year, so you are close. There is no harm in booking now and asking what an evaluation would involve — appointments take time to come through, and being early costs nothing.

If it's this, not that

Still not sure

This page is the general answer. Yours is a specific child.

The advisor can be. It has read everything here, and it knows how old your children actually are — which is the whole difference wherever guidance changes with age. Ask it anything.

She's got a temperature of 100. Is that something to worry about?
He's obsessed with space and galaxies — what toys are worth getting him?

Get the weekly note — and the advisor

Free. It comes with the note.

It answers from the same cited pages you are reading, and when the question is where to go, from the real clinician, hospital and childcare records behind this site — not a link to go search them yourself. It says so when we have not written about something, and it is not a doctor; for anything urgent it gives you the threshold and tells you to call.

Where this comes from

Does my age affect my fertility?ASRM
A fertility specialist on egg quality and trying after 40Natalie Crawford, MD

Every claim on this page traces to one of these. See every source we use →

Written from the sources named above, and it is not a substitute for your own doctor. If something feels wrong to you, that instinct is a good enough reason to call — you know yourself and this family better than any page does.