First Trimester of Pregnancy

During the first trimester alone your baby changes from a single fertilized cell to the embryo that implants itself in your uterine wall to a peach-sized bundle of growing limbs and body systems. So much happens in so little time: Seven weeks into your pregnancy, or five weeks after conception, your baby's brain and face are rapidly developing. Tiny nostrils become visible, and the eye lenses begin to form. The arm buds that sprouted last week now take on the shape of paddles. Organs take shape, baby starts to move (around week eight of pregnancy), and hair follicles and nail beds form. More major first-trimester milestones include the formation of muscles, the production of white blood cells to fight off germs, and the development of vocal cords.