Basal body temperature charting is one of the oldest fertility tools — and one of the most abandoned, because it demands a thermometer and a wake-up time worthy of a monastery.
Why temperature matters
After ovulation, progesterone raises your baseline body temperature by roughly 0.2–0.5°C. Sustained warmth confirms the fertile window has passed; the transition marks it. It's the clearest retrospective marker of ovulation your body offers.
The problem was never the signal
The signal is excellent. The collection method was the problem: one manual measurement a day, vulnerable to illness, alcohol, late nights and forgetful mornings.
What continuous measurement changes
Measured overnight from fabric against your skin, temperature becomes a curve, not a point:
- Transitions become visible even when single readings are noisy.
- Illness or disrupted sleep stop ruining whole cycles of data.
- Patterns across cycles emerge — your personal thermal fingerprint.
That's why skin temperature is the anchor signal in Femora's five-signal approach, collected while you sleep and interpreted with the other four.
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