Pregnancy

A pregnancy is divided into three phases, called trimesters. Each trimester has its own significant milestones. The first trimester is the most fragile period, during which all major organs and systems are formed. Most birth defects and miscarriages occur during the first trimester. During the second and third trimester, the fetus is fully formed and grows and matures rapidly. The trimesters are divided as follows:

• first trimester
  0 to 12 weeks
• second trimester
  13 to 28 weeks
• third trimester
  29 to 40 weeks

(However, some authorities use the 42 weeks method divided by 3 trimesters with the 1st trimester, 0 - 13 weeks; the 2nd trimester, 14 - 28 weeks; and the 3rd trimester, 29 - 42 weeks.)

Listed in the directory below, you will find additional information regarding the three phases of pregnancy, for which we have provided a brief overview. 

If you cannot find the information in which you are interested, please visit the Pregnancy & Childbirth Online Resources page in this Web site for an Internet/World Wide Web address that may contain additional information on that subhead.

Get indepth information on these additional topics on OHSUhealth.com

• Anatomy: Fetus in Utero
• The First Trimester (0 - 12 Weeks)
• The Second Trimester (12 - 24 Weeks)
• The Third Trimester (24 - 40 Weeks)
• The Pregnant Mother
• Hormones During Pregnancy
• Weight Gain During Pregnancy
• Nutrition During Pregnancy
• Exercise During Pregnancy
• Work and Pregnancy
  
• Sex During Pregnancy
• Sleeping During Pregnancy

Childbirth Services at OHSU

Back to childbirth & Pregnancy Index

Back to Center for Women's Health Home