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Home > Health Library > Trimester
A normal pregnancy lasts about 40 weeks from the first day of your last menstrual period to the birth of a baby. This time is roughly divided into 3 periods: the first trimester, from the first day of your last menstrual period to about the 12th week of pregnancy; the second trimester, from about 13 to 27 weeks of pregnancy; and the third trimester, from about 28 weeks of pregnancy until birth.
Each trimester of pregnancy is marked by developmental changes in the fetus.
Current as of: February 11, 2020
Author: Healthwise Staff
Medical Review:Sarah A. Marshall, MD - Family Medicine & Adam Husney, MD - Family Medicine & Kirtly Jones, MD - Obstetrics and Gynecology, Reproductive Endocrinology
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