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first trimester
During the first trimester alone your baby changes from a single fertilized cell (a zygote), to the embryo that implants itself in your uterine wall, to a peach-sized bundle of growing limbs and body systems. Organs take shape, and baby starts to move. -
first trimester
Baby’s bones: By about week 6, baby starts to sprout arms, legs, hands and feet — and fingers and toes around week 10.
Hair and nails: Skin begins forming between weeks 5 and 8, with hair follicles and nail beds forming around week 11. -
first trimester
Digestive system: By about week 8, baby’s intestines will begin forming, and your baby will have already gone through two sets of kidneys (with the third and final set on its way!).
Sense of touch: Your baby will have touch receptors on his face (mostly lips and nose) around week 8. By week 12, he’ll have receptors on his genitals, palms and the soles of his feet. -
first trimester
Eyesight: Optic nerves (which pass info from the eyes to the brain and back) and lenses begin to form by week 4, with the retina beginning to form around week 8.
Heart: By week 5, the tube that will become your baby’s heart begins to beat spontaneously. It will become stronger and more regular — and you’ll be able to hear it! — around week 9 or 10 (though sometimes later, depending on your baby’s position in your uterus).