How it works
Use a known due date, the first day of the last menstrual period, a known conception date, ultrasound gestational age, or an IVF transfer date. Each method is converted to a 40-week pregnancy timeline.
Input query strings and outputs
Use an input name in this page’s URL as ?name=value, and join additional inputs with &. Portable shared links may instead use the compact ?ac= state parameter.
Input query strings
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?method=Dating methodChoice · Required · Default: lmp · Accepted values: due, lmp, conception, ultrasound, ivf
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?dueDate=Known due dateDate · Required · Default: 2027-03-08 · Used when method = due
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?lmpDate=First day of last menstrual periodDate · Required · Default: 2026-06-01 · Used when method = lmp
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?cycleLength=Average cycle lengthNumber · Required · Default: 28 · Used when method = lmp
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?conceptionDate=Known conception dateDate · Required · Default: 2026-06-15 · Used when method = conception
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?ultrasoundDate=Ultrasound dateDate · Required · Default: 2026-08-24 · Used when method = ultrasound
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?ultrasoundWeeks=Gestational age at ultrasound: weeksNumber · Required · Default: 12 · Used when method = ultrasound
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?ultrasoundDays=Additional daysNumber · Required · Default: 0 · Used when method = ultrasound
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?transferDate=Embryo transfer dateDate · Required · Default: 2026-06-20 · Used when method = ivf
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?embryoAgeDays=Embryo age at transferChoice · Required · Default: 5 · Accepted values: 3, 5, 6 · Used when method = ivf
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?asOfDate=Calculate pregnancy progress as ofDate · Required · Default: current date
Outputs
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dueDateResultEstimated due dateDate · Primary output
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gestationalAgeGestational ageText
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trimesterTrimesterText
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conceptionDateResultEstimated conception dateDate
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lmpDateResultEstimated LMP dateDate
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daysRemainingDays until estimated due dateWhole number
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termWindowEstimated term windowText
Not a clinical determination
A clinician may revise dating based on records and ultrasound. The displayed milestones and term window are planning estimates.