Daily fertility likelihood labels that never say safe #23

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opened 2026-08-18 14:44:42 -05:00 by null · 0 comments

null commented

2026-08-18 14:44:42 -05:00

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§18 asks for today's fertility estimate as a label, and gives the vocabulary: Lower likelihood, Higher likelihood, Estimated fertile window.

It also gives the prohibition, in three words: "Avoid 'safe' or 'unsafe' labels."

That is not squeamishness about wording. A person reading "safe" on a day outside the fertile window will take a decision on it, the estimate is derived from a predicted date that carries days of uncertainty, and the app has already promised in §18 that none of this is contraception. "Lower likelihood" is true; "safe" is a claim the model cannot support and the product must never make.

Build the label as a function of the day relative to the estimate, so it is testable, and show it on Today under the existing fertility section.

Also worth pinning here: a day can be outside the fertile window and still not be "lower likelihood" if the forecast is barely certain at all. Where confidence is low the honest label is the vaguer one.

Verify: a unit test maps days across a cycle to the three labels; no label string in the codebase contains "safe"; and the label on Today changes as the estimated window is entered and left.

§18 asks for today's fertility estimate as a label, and gives the vocabulary: **Lower likelihood**, **Higher likelihood**, **Estimated fertile window**. It also gives the prohibition, in three words: *"Avoid 'safe' or 'unsafe' labels."* That is not squeamishness about wording. A person reading "safe" on a day outside the fertile window will take a decision on it, the estimate is derived from a predicted date that carries days of uncertainty, and the app has already promised in §18 that none of this is contraception. "Lower likelihood" is true; "safe" is a claim the model cannot support and the product must never make. Build the label as a function of the day relative to the estimate, so it is testable, and show it on Today under the existing fertility section. Also worth pinning here: a day can be *outside* the fertile window and still not be "lower likelihood" if the forecast is barely certain at all. Where confidence is low the honest label is the vaguer one. Verify: a unit test maps days across a cycle to the three labels; no label string in the codebase contains "safe"; and the label on Today changes as the estimated window is entered and left.