# The scan lesson, and a date I got wrong in my own reference card

Lesson 6 (5 Sep 2026, Pud Pud 4+6) = the dating scan. Chosen over the money follow-up because L6-money is still blocked on both inputs (accountant, Herman Miller) and the scan is the only genuinely **time-boxed** thing in the workspace.

## The correction that became the lesson
`reference/antenatal-timeline.html` said the dating scan window was **11–25 Oct 2026** — which is 10+0 to 12+0, and wrong in a way that costs something. The combined test requires **CRL 45.0–84.0 mm = 11+2 to 14+1**, i.e. **20 Oct – 9 Nov 2026**. A scan on 11–19 Oct is a perfectly good dating scan that silently loses the screening.

That gap *is* the lesson's win: one sentence to say at the booking desk. It is exactly the shape that works for him — a specific, dated, actionable thing nobody else is checking. Timeline row rewritten; a quadruple-test fallback row (14+2–20+0 = 10 Nov–20 Dec) added so the consequence of missing it is on the card too.

**Pattern to keep:** open with the correction rather than quietly patching the reference doc. Same call as L5 §1. He argues from first principles and would find a silent retcon corrosive.

## Design decisions
- **EDD framed as load-bearing, not sentimental.** The table of things pinned to it (QW, MATB1, earliest leave, anomaly scan) ends on the one that bites: a *later* EDD shrinks the 19-day gap to her fixed 28 May contract end. Money and pregnancy taught as one system.
- **Miscarriage numbers given plainly** (10% at 6–7 wks with heartbeat → 98% at 8 → 99.4% at 10; 3–4% second trimester) and used to explain *why* twelve weeks is the telling point — the curve, not superstition. Then converted into a decision they must make before the scan: who to tell, when, who tells them. Noted that her employer deadline (end of QW, 30 Jan 2027) creates no pressure.
- **"Watch her, not the screen."** The behavioural beat of the lesson, same slot as L4's leave-the-room fact.
- Spacing: the L5 £16,000 dividend-headroom question.

## Verified this session
- CRL 45.0–84.0 mm / 11+2–14+1; quad test HC 101–172 mm, bloods 14+2–20+0; 1 in 150 cut-off — NHS FASP handbook.
- EPAU **01925 662320** re-confirmed (the trust's own gynaecology page lists 01925 662063 for a general gynae line — 662320 is the EPAU number and stands). Antenatal appointments 01925 662260.
- Glossary EPU entry corrected from "under 20 weeks" to the trust's real 18-week split. It had contradicted the red-flags card since L5.

## Open
- Herman Miller enhanced maternity scheme + repayment clause — still the highest-value unknown.
- Accountant's reply.
- Booking appointment date (window opened 27 Sep... not yet reached).
- Symptoms: sickness would typically start around now (~5 weeks). Asked again.

## Next
Recompute every date in the workspace the day the scan EDD lands. Queued lessons: wills + guardianship (unmarried, needed before May 2027), second trimester, money follow-up.