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Home > Be Healthy > 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 13th week of pregnancy; the second trimester, from about 14 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: June 16, 2021
Author: Healthwise Staff
Medical Review:Sarah Marshall MD - Family Medicine & Adam Husney MD - Family Medicine & Kirtly Jones MD - Obstetrics and Gynecology & Heather Quinn MD - Family Medicine
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