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Dating Pregnancy from the Last Menstrual Period

Purpose:

To estimate the duration of pregnancy using 266 days from the date of conception (or 280 days from the first day of the last menstrual period [LMP]).

Specialty:

Obstetrics & Gynecology

Objective:

other testing, informed consent, exercise, travel

ICD-10:

Z34

Description:

Obstetricians usually date pregnancies in weeks, typically from the first day of the last menstrual period. Since fertilization occurs 2 weeks after this date, after a new ovum is released, obstetric dates are about 2 weeks longer than embryologic dates.

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