Due Date Calculator API

Estimated pregnancy due date (40 weeks) from the last period, conception date or IVF transfer, with milestone dates and the gestational age on a given day.

POST /api/v1/tools/due-date-calculatorMCP due_date_calculatorTime & Date

Estimate a pregnancy due date from the last period, conception date or IVF transfer, with how many weeks along you are, the trimester and key dates.

Input

Send these as a JSON object. Unknown fields are rejected.

method: lmp: first day of the last menstrual period. conception: conception date. ivf: embryo transfer date. (string, one of lmp, conception, ivf, default "lmp")
date: The LMP, conception or transfer date as YYYY-MM-DD. (string, up to 10 characters, required)
cycleLength: LMP method only: average cycle length in days (20 to 45). (integer, 20 to 45, default 28)
embryoDays: IVF only: embryo age at transfer, 3 or 5 days. (integer, 3 to 5, default 5)
asOf: Optional date (YYYY-MM-DD) to report the gestational age and trimester on. (string, up to 10 characters)

Try it in the browser JSON Schema Get an API key

curl https://pithlab.com/api/v1/tools/due-date-calculator \n  -H "Authorization: Bearer $PITHLAB_KEY" \n  -H "Content-Type: application/json" \n  -d '{"method":"lmp","date":"2026-03-01","asOf":"2026-10-20"}'