Source: https://guthlabs.ai/docs/instruments/pregnancy-due-date-calculator/

instrument / verified-clean

# Pregnancy Due Date Calculator

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Inspectable records

[01**Overview**Purpose and lifecycle](<https://guthlabs.ai/docs/instruments/pregnancy-due-date-calculator/>)[02**Mechanism**Method and assumptions](<https://guthlabs.ai/docs/instruments/pregnancy-due-date-calculator/mechanism/>)[03**Implementation**Binding and validation](<https://guthlabs.ai/docs/instruments/pregnancy-due-date-calculator/implementation/>)[04**Qualification**Evidence and errata](<https://guthlabs.ai/docs/instruments/pregnancy-due-date-calculator/qualification/>)

## Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

**Area**: Biology, Medicine & Pharmacology (educational estimates only — every panel labeled not-medical-advice)

**Tranche**: tranche-4

**Evidence ID**: t4-242

**Ledger rows**: 1

No ledger note is attached.

## Review findings

The due-date formulas are standard estimates, but the specification is incomplete for the claimed gestational-age and ultrasound-dating features. Exact ambiguities requiring resolution are: missing as-of/current date; missing ultrasound dating formula and input schema; unspecified conception-to-gestational-age convention; unspecified trimester boundaries; and unspecified handling of menstrual-cycle-length adjustments. The educational, not-medical-advice label is appropriate and should remain prominent on every result.

### Formula and scope findings

- Naegele's rule, LMP + 280 calendar days, is standard only when LMP day 1 is known and a conventional 28-day cycle is assumed; cycle-length or ovulation adjustments are not specified.

- Conception date + 266 calendar days is a standard estimated due-date formula.

- The specification does not provide a formula or required input format for ultrasound dating, despite listing it as an input method.

- Gestational age requires an as-of/current date, which is not listed among the inputs. For conception dating, the specification also does not state whether gestational age is conventionally conception date plus 14 days.

- Trimester calculation is claimed but no trimester boundary convention is specified. The test vectors assume first trimester is 0w0d through 13w6d, second is 14w0d through 27w6d, and third begins at 28w0d.

### Unit assumptions

- All date additions and differences use calendar days, not business days or elapsed 24-hour periods.

- A gestational week is exactly 7 days; outputs use completed weeks and remaining days.

- LMP is treated as the first day of the last menstrual period.

- For conception dating, gestational age is conventionally calculated as conception date plus 14 days.

- Dates are interpreted as local calendar dates in ISO YYYY-MM-DD format, with no time-zone conversion.

- Naegele's LMP formula assumes a 28-day cycle; adjustments for longer or shorter cycles are not applied.

## Boundary hardening

**BREAK_CLAIMED** · SELF_FLAGGED

An extreme but valid-at-the-input-boundary JavaScript Date produces a due date beyond the representable Date range and must be rejected or reported as undefined. Additionally, an unlabelled slash-formatted date yields materially different results under MM/DD versus DD/MM conventions.

## Errata and corrections

No applied erratum is attached to this unique-name record.

## Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

````
{
  "inputs": {
    "dating_method": "LMP",
    "last_menstrual_period": "2025-01-01",
    "as_of_date": "2025-02-12"
  },
  "expected_outputs": {
    "estimated_due_date": "2025-10-08",
    "gestational_age": "6w0d",
    "trimester": 1
  },
  "working": "Due date: 2025-01-01 + 280 days = 2025-10-08. Gestational age: 2025-02-12 - 2025-01-01 = 42 days. 42 / 7 = 6 weeks with 0 days remaining, so 6w0d. Since 6w0d is before 14w0d, trimester = 1."
}
````

## Related workflows

[Pregnancy & Cycle SuiteLMP dating](<https://guthlabs.ai/docs/instrument-workflows/cycle-suite/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`

- `evidence-tranche4/tranche4-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`