Your 20s: Peak Biology, Peak Flexibility
Monthly conception probability: ~25–30%. Miscarriage rate: ~10–15%. Egg quality: at its biological peak. This is the decade with the widest margin for error — less-than-perfect timing, less-than-perfect lifestyle, and conception still happens at high rates.
What to do: If you’re not ready for kids yet, this is the best time to invest in reproductive health for the future. Start a prenatal vitamin (yes, even now — folate stores build over time). Get a baseline check of thyroid function and vitamin D. Consider egg freezing if your timeline is uncertain and you can afford it — freezing at 25 gives you dramatically better outcomes than freezing at 35.
30–34: Still Strong, Start Being Strategic
Monthly probability: ~20–25%. Miscarriage rate: ~15–20%. Egg quantity is declining but quality remains high. Most women in this range conceive within 6–9 months of trying.
What to do: Start a prenatal 3 months before TTC. Add CoQ10 (200mg daily) to support egg quality. Track ovulation with OPKs. Get bloodwork: AMH, FSH, TSH, vitamin D. If no conception after 12 months, see an RE.
35–37: The Acceleration Zone
Monthly probability: ~15–20%. Miscarriage rate: ~20–25%. Egg quality decline begins to accelerate. This is where the “35 cliff” narrative comes from — but the data shows a slope, not a cliff. See FertileStart’s fertility cliff myth-buster.
What to do: Everything in the 30–34 section, plus: increase CoQ10 to 400–600mg daily. See an RE after 6 months (not 12). Consider getting an AMH test proactively. For him: semen analysis as a baseline. Supplements and lifestyle optimization become higher-ROI because you have less margin.
38–40: Time-Sensitive
Monthly probability: ~10–15%. Miscarriage rate: ~25–35%. Chromosomal abnormality rates in eggs increase significantly. This is where the data genuinely shifts — the decline from 37 to 40 is steeper than from 30 to 37.
What to do: See an RE after 3–6 months. Full workup: AMH, FSH, AFC, HSG, semen analysis. Be open to treatment options — IUI and IVF success rates are still solid in this range. CoQ10 at 400–600mg, DHEA (25mg 3x/day — only with RE supervision), and aggressive lifestyle optimization.
40+: Possible, But Plan for Help
Monthly probability: ~5–10%. Miscarriage rate: ~30–40%. Natural conception is absolutely possible but takes longer on average. Many couples benefit from IVF with PGT-A testing (to screen embryos for chromosomal normality).
What to do: See an RE immediately — don’t wait months of trying. Every month counts at this stage. Full workup plus frank conversation about options: natural TTC with monitoring, IUI, IVF, donor eggs. The financial side: see ConceiveGuide’s insurance guide and grants directory.