Fertility by Age Calculator

Age is the single strongest predictor of fertility that research has identified — but "strongest predictor" doesn't mean "the only thing that matters," and population statistics describe averages, not individual outcomes. This calculator shows monthly and cumulative conception chances, miscarriage risk, and IVF success rates by age, drawn from clinical reference data still cited by reproductive health organizations today.

How fertility changes with age

These figures reflect fecundity — the probability of conception in any given cycle with regular, unprotected intercourse — and they’re consistent with what reproductive health organizations like ASRM still cite in current patient education materials. The underlying biology is well understood: women are born with all the eggs they’ll ever have, and both egg quantity (ovarian reserve) and egg quality decline progressively over a reproductive lifetime, accelerating in the late 30s and 40s.

Egg quantity and egg quality decline for related but distinct reasons, both worth understanding. Quantity declines simply because the finite supply of eggs present at birth is gradually depleted through ovulation and background cell loss over decades — by the time of menopause, the original supply of roughly one to two million eggs has been reduced to essentially none. Quality declines separately, driven mainly by an increasing rate of chromosomal abnormalities in the remaining eggs as they age within the body for longer — this quality decline is the primary driver of both reduced conception chances and elevated miscarriage risk at older ages, more so than quantity alone.

How this calculator works

This formula treats each month as an independent trial with the same probability — a standard simplifying model used in reproductive epidemiology (sometimes called a fecundability model), even though real month-to-month probability isn’t perfectly constant for any individual. It’s a reasonable approximation for population-level statistics, which is what this calculator provides: a starting reference point based on your age bracket, not a personal prediction.

Worked example

Using this calculator’s own default example — age 32, just starting to try:

The 12-month cumulative figure shown directly in this calculator’s dataset for this age bracket (80%) is drawn from population studies rather than recalculated purely from the monthly rate — the two numbers are close but not always identical, since real-world cumulative studies capture some of the imperfect month-to-month independence the simplified formula assumes away.

Is the decline really that sharp?

This is worth addressing directly, because there’s genuine, active scientific discussion about it. The commonly repeated narrative — including in much patient-facing material — describes a “cliff” around age 35, with fertility falling sharply and suddenly at that point. Some methodologically strong research pushes back on how sudden that specific transition really is.

A separate, more recent analysis (Geruso et al., 2023) found fecundity declining roughly linearly from age 20 to 40, without a sudden acceleration specifically in the mid-30s — with the drop from 20 to 25 comparable in size to the drop from 35 to 40, contrary to the common belief that the 20s are largely stable and the 30s bring a sudden change. Other large cohort data (a study of nearly 3,000 couples) found fecundability relatively stable across ages 28–33, with the more pronounced decline concentrated later, in the late 30s and 40s.

Why does this matter, and why do sources disagree? Much of the traditional “sharp decline at 35” narrative traces back to older data — including historical demographic records and studies of fertility-clinic populations, both of which can overstate age-related decline compared to general, healthy populations trying to conceive. Newer cohort studies specifically designed to avoid these biases tend to find a somewhat more gradual, more linear pattern. This calculator uses the more traditional, still-widely-cited clinical figures (consistent with current ASRM patient materials) since they remain the standard reference most healthcare providers and patients encounter — but it’s worth knowing that some rigorous recent research suggests the true picture, especially through the early-to-mid 30s specifically, may be somewhat less dramatic than the numbers above convey on their own.

None of this means age doesn’t matter, or that the decline reverses or stops — every study cited here, including the more optimistic ones, still finds a real, meaningful decline in fertility with age, particularly from the late 30s onward. The disagreement is specifically about the shape and timing of that decline through the 30s, not about whether it happens at all. Presenting both perspectives here is meant to give a more complete, honest picture — not to suggest age doesn’t matter, and not to dismiss the genuine, well-documented decline that does occur, particularly for anyone in their late 30s or 40s.

What affects monthly conception chances beyond age

Age is the strongest single predictor research has identified, but it’s far from the only factor. Research on modifiable (“volitional”) factors found that couples in the most favorable category for frequency of intercourse, contraceptive history, and cycle timing had an estimated 88% probability of conceiving — a reminder that individual behavior and circumstances meaningfully interact with age-related statistics rather than being overridden by them entirely.

Miscarriage risk and age

Miscarriage risk rises with age largely for the same underlying reason conception chances fall: egg quality declines, and a growing share of eggs carry chromosomal abnormalities incompatible with a viable pregnancy as women get older. This is a distinct statistic from conception chances — someone can conceive relatively easily and still face a higher chance of early pregnancy loss, which is part of why age-related fertility conversations usually address both figures rather than conception alone.

The figures in this calculator’s chart broadly track a well-cited pattern: miscarriage risk roughly doubling between the 20s and late 30s, and climbing further into the 40s. These are population averages from large studies; an individual’s actual risk in any specific pregnancy depends on additional factors a general age-based statistic can’t capture, including the outcome of any prior pregnancies, underlying health conditions, and factors specific to that particular conception that aren’t visible from age alone.

IVF success rates by age

IVF live birth rates follow the same general age-related pattern as natural conception, for the same underlying reason — egg quality and quantity, not the fertilization method itself, drive most of the age effect. The figures shown here come from CDC/SART national reporting, the authoritative source for U.S. clinic outcomes.

One important caveat: the “44+” bucket shown is broader than it should ideally be. A 2023 study specifically disaggregating this age band found cumulative live birth rates of roughly 8.6% at age 44 and 5.0% at 45, dropping to 1.3–3.6% by ages 48–50 — a real, meaningful difference the flat “3%” figure in a single “44+” bucket doesn’t capture. Anyone in this age range is especially well served by an individualized consultation rather than relying on a single broad-bucket statistic, since where within that range someone falls matters considerably more here than at any younger age.

It’s also worth understanding what “success rate” actually measures in IVF reporting, since it varies by report and can be a source of confusion when comparing numbers from different sources. Rates can be reported per cycle started, per egg retrieval, per embryo transfer, or as a cumulative rate across multiple cycles — and these produce meaningfully different numbers for the exact same underlying population. The figures in this calculator represent a general per-cycle reference; anyone evaluating a specific clinic’s reported success rates should confirm which of these definitions is being used, since “success rate” without that context can be genuinely misleading when comparing sources.

Donor eggs meaningfully change this picture for anyone considering that path — because donor eggs typically come from younger donors, live birth rates using donor eggs remain relatively high and stable across the recipient’s age, since the age-related decline in outcomes tracks the age of the egg, not the age of the person carrying the pregnancy. This is worth knowing as a genuine option that exists outside the age-based curve shown in this calculator’s own-egg IVF figures.

When to seek help

Standard guidance suggests seeking a fertility evaluation after 12 months of regular, unprotected intercourse without conception for those under 35, or after 6 months for those 35 and older — the shorter window for the older group reflects both the faster pace of age-related decline and the reduced time available to pursue treatment if needed. About 15% of couples meet the clinical definition of infertility (failing to conceive after 12 months of trying), which is common enough that seeking evaluation is a normal, unremarkable step rather than a rare or last-resort one.

Earlier evaluation is reasonable regardless of these general timelines for anyone with a known risk factor — irregular or absent periods, a history of pelvic infection or endometriosis, prior chemotherapy or pelvic radiation, or a partner with a known fertility issue. As with every statistic on this page, these are general guidelines meant to prompt a conversation with a doctor, not a substitute for one — individual circumstances can reasonably shift what timeline makes sense for a specific person or couple.

A fertility evaluation itself is a fairly standard, well-established process rather than something to feel apprehensive about starting — it typically begins with a review of medical and cycle history, followed by relatively simple initial testing (bloodwork to assess ovarian reserve and hormone levels, a semen analysis for a male partner, sometimes imaging to check the uterus and fallopian tubes) before any more involved treatment is considered. Starting this process doesn’t commit anyone to a specific treatment path — it’s an information-gathering step that helps clarify what, if anything, is affecting a couple’s specific chances, which is useful information regardless of what path is chosen afterward.