OB Datum: Pregnancy Dating

Free LMP, conception and known-EDD dating. Lifetime Pro adds known GA, IVF, reconciliation, Health import and unlimited anonymous cases.

Calculate and compare pregnancy dates with a clear explanation of every result.

OB Datum is a clinician-first pregnancy-dating workspace for iPhone and iPad. It performs deterministic calendar arithmetic and shows the source, formula, equivalent dates, and calculation-engine version for review.

CALCULATE FROM

• First day of the last menstrual period, with optional regular-cycle adjustment • Documented conception or ovulation date • An established estimated due date

Lifetime Pro adds calculations from gestational age documented on a known date and from an IVF embryo-transfer date and embryo age.

LIFETIME PRO

One purchase—with no subscription or advertising—unlocks known-GA and IVF/ART dating, read-only Health import, full dating reconciliation, unlimited anonymous saved cases, formatted sharing, Calendar export, and custom timeline milestones.

In Reconcile, keep an established EDD locked while comparing the dates implied by LMP, ultrasound gestational age, and IVF/ART. OB Datum reports signed calendar-day differences and never changes or averages dates automatically. Guideline-based redating thresholds remain unavailable until the app's versioned clinical profile completes independent review.

EXPLORE THE TIMELINE

Calculate gestational age on a selected date, find the date corresponding to a gestational age, review descriptive milestones, and explore an interactive pregnancy wheel with accessible day and exact-date controls.

PRIVATE BY DESIGN

• No advertising or tracking • No patient names, record numbers, contact details, or notes • Anonymous saved calculations stay protected on your device • Optional Pro read-only import of the latest menstrual-cycle start from Health • Pro Calendar export includes only the EDD and no patient identifiers • The widget opens OB Datum without displaying pregnancy or case data

OB Datum also provides a privacy-safe due-date action for Shortcuts, shareable calculation summaries, dark mode, Dynamic Type, VoiceOver support, and Reduce Motion support.

OB Datum supports date arithmetic and clinical review. It does not diagnose, prescribe, select a delivery date, or replace professional judgment. Independently verify every input, result, and source before clinical use.