Estimate natural and IVF pregnancy rates by age. Includes cumulative probability, miscarriage and aneuploidy risk, AMH interpretation, and time-to-conceive milestones.
The Fertility by Age Calculator estimates natural conception probability, IVF success rates, miscarriage risk, and chromosomal aneuploidy rates based on maternal age. Female fertility peaks in the early-to-mid 20s, begins declining gradually around age 30, and declines more steeply after 35. By age 40, per-cycle pregnancy rates are roughly one-fifth of peak fertility, and by 43–44, natural conception becomes uncommon.
The calculator uses published population-level fertility data from multiple sources including SART (Society for Assisted Reproductive Technology) IVF statistics, Heffner (2004) natural fecundity curves, and ACOG age-specific miscarriage rates. It computes cumulative probability across multiple cycles using the geometric model, and adjusts for modifiable factors including cycle regularity, partner age, and BMI.
Critically, age-related fertility decline is primarily driven by increasing chromosomal aneuploidy (abnormal chromosome number) in eggs. At age 25, approximately 5% of eggs are aneuploid; by 40, this rises to ~47%. Aneuploidy causes most early pregnancy losses and is the main reason both natural and IVF pregnancy rates decline with age. Understanding this biology helps frame realistic expectations and informs decisions about fertility testing, treatment timing, and egg freezing.
Understanding how age affects fertility helps with family planning decisions, setting realistic expectations, and knowing when to seek specialist evaluation. The calculator integrates multiple data points (natural rates, IVF rates, miscarriage, aneuploidy) into a single view, and adjusts for individual factors that many static charts ignore. Keep these notes focused on your operational context.
Per-cycle pregnancy rate: Age-specific from published data (population averages) Cumulative probability = 1 − (1 − p)^n Where p = per-cycle probability, n = number of cycles Adjustments: • Irregular cycles: ×0.7 (reduced ovulation frequency) • Partner age >40: ×0.92; >45: ×0.85 • BMI >30: ×0.85; >35: ×0.75; <18.5: ×0.80 Time to milestone = ln(1−target) / ln(1−p)
Result: Per-cycle: 12%, Cumulative (12 mo): 78.5%, Miscarriage risk: 22%
At 35, per-cycle natural conception rate is ~12%. Over 12 cycles: 1−(1−0.12)^12 = 78.5% cumulative probability. Miscarriage risk at 35 is ~22%, making the per-pregnancy live birth rate ~9.4%. IVF success rate is ~33% per transfer. The 22% aneuploidy rate explains much of the decline from peak fertility. Partner age 37 has minimal impact.
Female fertility is limited by egg quantity and quality, both of which decline with age. Women are born with ~1–2 million eggs; by puberty, this drops to ~300,000–400,000. Only ~400 eggs are ovulated during a lifetime. The decline in egg number accelerates after 37 (the "critical threshold"), and most women have <1,000 remaining eggs at menopause (~51). Egg quality — specifically the rate of chromosomal errors during meiosis — is the dominant factor. The "cohesion fatigue" hypothesis suggests that proteins holding chromosomes together during the decades-long arrest between fetal life and ovulation gradually degrade, increasing the risk of meiotic errors.
While female age receives most attention, male factor infertility is present in ~40% of infertile couples. Unlike eggs, sperm are produced continuously, but the process is imperfect: DNA fragmentation increases with age, sperm concentration declines (~1% per year after 40), and de novo genetic mutations accumulate (~2 per year). Modifiable factors affecting sperm quality include: heat exposure (tight clothing, laptops, hot tubs), medications (testosterone, finasteride, SSRIs), lifestyle (smoking, heavy alcohol, obesity), and environmental exposures (pesticides, BPA). A semen analysis is one of the first tests in any fertility evaluation.
The stepped approach to treatment typically follows: 1) Timed intercourse with monitoring (3–6 cycles), 2) Clomid/letrozole + IUI (3–4 cycles), 3) Injectable gonadotropins + IUI (2–3 cycles), 4) IVF. However, this stepwise approach is age-dependent: women over 38 may benefit from moving to IVF sooner (within 3–6 months), as IUI success rates decline significantly with age while IVF can be augmented with PGT-A (preimplantation genetic testing) to select chromosomally normal embryos, partially offsetting the age-related decline.
Fertility begins declining gradually in the early 30s, with the decline accelerating after 35. Key inflection points: at 30, per-cycle rate is ~20% (vs. 25% at peak); at 35, it drops to ~12%; at 40, to ~5%; and at 43+, to ~2%. The 35–40 window represents the steepest decline. However, these are averages — some women maintain good fertility into their early 40s while others experience premature decline in their 30s. Ovarian reserve testing (AMH, AFC) provides individual-level information.
Yes, though less dramatically than maternal age. Sperm quality gradually declines after 40: decreased motility, increased DNA fragmentation, and longer time to conception. Studies show men over 40 have ~30% lower per-cycle conception rates compared to men under 30. Paternal age >40 is also associated with modestly increased risks of autism spectrum disorder, schizophrenia, achondroplasia, and certain birth defects. Unlike egg production, sperm production continues throughout life, but quality diminishes.
AMH (Anti-Müllerian Hormone) reflects the number of remaining eggs (ovarian reserve). Normal ranges decrease with age — the same AMH value has different meanings at different ages. It's most useful for: predicting IVF response (low AMH → fewer eggs retrieved), identifying premature ovarian insufficiency, and general fertility counseling. Important limitations: AMH doesn't predict egg quality or natural conception probability, varies between labs, and can be suppressed by hormonal contraceptives. It's one piece of the puzzle, not a fertility crystal ball.
Dramatically so. IVF success depends primarily on the egg age (not uterine age). A 42-year-old using donor eggs from a 25-year-old has success rates comparable to a 25-year-old using her own eggs (~50% per transfer). This is strong evidence that egg quality — specifically chromosomal normalcy — drives age-related fertility decline. This is also why egg freezing is most effective when done at younger ages, and why donor eggs are highly successful for older patients.
Egg freezing is most effective when done before 35, as egg quality and quantity are higher. The optimal window is generally considered 25–35. After 38, both the number of eggs retrieved and their quality decline significantly, reducing the value proposition. Key considerations: cost ($10–15K per cycle + annual storage), number of eggs needed (typically 10–20 mature eggs for reasonable probability), and your timeline. ACOG states that egg freezing is no longer considered experimental and clinicians should discuss it as an option during reproductive counseling.
Population-level data provides reasonable estimates for counseling and planning but cannot predict individual outcomes. Key limitations: they don't account for tubal patency, uterine anatomy, endometriosis, male factor, ovulatory function, or genetic factors. A couple with a normal fertility evaluation may have higher-than-average rates; someone with undiagnosed endometriosis may have significantly lower rates than the age-based average. Use these calculators for general guidance and discuss personal factors with a reproductive specialist.