Title: Pregnancy Guide, Stages of Pregnancy, Fetus Growth
Headings: Week-by-Week Pregnancy Guide
Week-by-Week Pregnancy Guide
Trimester One - Weeks One through 12
First Trimester Fetal Development
Trimester Two - Weeks 13 through 27
Second Trimester Fetal Development
Trimester Three - Weeks 28 through 40
Third Trimester Fetal Development
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Content: The cell group implants onto the uterine wall around day six, at which point it is referred to as an embryo. Implantation signals the beginning of pregnancy. Week Two: During week two, the cells of the implanted embryo multiply and differentiate. Week Three: The fetus's brain, spinal cord, heart, and digestive tract begin to form. Week Four: Rudimentary blood vessels begin to form, and the heart begins to beat. Week Five: The circulatory system further develops and becomes functional.