A normal pregnancy lasts about 40 weeks from conception to the birth of a baby. This time is roughly divided into 3 periods: the first trimester, from conception 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.
|Primary Medical Reviewer||Sarah Marshall, MD - Family Medicine|
|Specialist Medical Reviewer||Kirtly Jones, MD - Obstetrics and Gynecology|
|Last Revised||July 23, 2012|
WebMD Medical Reference from Healthwise