Normal pregnancy: First trimester

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Development of embryo in uterus at 8th week and fetus at 12th week.

The first trimester of pregnancy lasts from the first day of your last menstrual period through week 13.

Current as of: July 10, 2023

Author: Healthwise Staff
Clinical Review Board
All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.

The Health Encyclopedia contains general health information. Not all treatments or services described are covered benefits for Kaiser Permanente members or offered as services by Kaiser Permanente. For a list of covered benefits, please refer to your Evidence of Coverage or Summary Plan Description. For recommended treatments, please consult with your health care provider.