Conception comes down to a window of roughly six days each cycle — and that window moves, even in regular cycles. Hormone tracking replaces calendar guessing with observed signals: LH predicts ovulation a day before it happens, and PdG confirms afterward that it actually did. Together they turn a cycle from a mystery into a pattern.
What it is
Each cycle, FSH matures a follicle, estradiol rises, and a surge of LH triggers the egg’s release — ovulation. The egg lives about a day, but sperm survive up to five, so the fertile window spans the days before ovulation through the day after. After release, the empty follicle produces progesterone, which appears in urine as PdG. That sequence — surge, release, progesterone rise — is the whole measurable story.
Signs and symptoms
Some women notice ovulation: a day of one-sided twinge (mittelschmerz), clearer stretchy discharge, or a slight temperature shift after. Many notice nothing. Calendar apps estimate; bodies vary — which is why measured hormones outperform predictions, especially when cycles are irregular.
What you can track at home
LH strips, used daily around midcycle, catch the surge that says ovulation is likely within 24–36 hours — the highest-value days for conception. PdG strips in the following week confirm the cycle actually ovulated, which matters because surges without release do happen. A few cycles of both draws your personal pattern clearly — useful whether you’re trying to conceive now or simply want to know your body’s rhythm before you are.
When to see a doctor
See a provider if you’ve been trying for twelve months without success — six months if you’re 35 or older — or sooner if cycles are very irregular, absent, or your tracking shows LH surges without PdG confirmation across multiple cycles. Fertility conversations go better with data: months of tracked cycles give a provider a running start, and give you standing to push past “just keep trying.”
