How Fertility Actually Works
Most of what people absorb about fertility along the way is either vague or flat-out wrong. Here's the actual mechanics, so you know what you're working with.
Last updated August 2026
The monthly mechanics
Ovulation — when an egg is released — usually happens roughly in the middle of your cycle, though the exact timing depends on your cycle length. The egg survives about 24 hours, but sperm can survive up to 5 days, which means your realistic fertile window is about 6 days each cycle, not just one.
Tracking ovulation
Cycle tracking (our Cycle Tracker can help build this picture over time), ovulation predictor kits, and changes in cervical mucus can all help identify your fertile window in real time. Basal body temperature is a useful confirmation that ovulation happened, but it rises after the fact — a lagging indicator, not a predictor.
When to seek an evaluation
The standard guidance: under 35, it's reasonable to try for 12 months before an evaluation; 35–39, that window shortens to 6 months; 40 and older, evaluation is recommended right away rather than waiting. Certain conditions (irregular cycles, endometriosis, prior pelvic surgery) can move that timeline up regardless of age. Our Fertility Evaluation walks through your specific history in more depth if you're at that point.
What can affect fertility
Age, ovulation regularity, tubal health, and uterine factors all play a role — and so does male factor, which contributes to roughly 40–50% of infertility cases. It's worth normalizing that this isn't only ever “a woman's problem”; ASRM recommends evaluating both partners from the start.
Worth discussing with your provider
Educational information only — general patterns that vary by person. This is not medical advice, a diagnosis, or a substitute for care from your own clinician.
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