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Period: to
First Trimester
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4 Weeks
Brain and spinal cord have began to form, as well as the heart, and arm and leg buds appear. -
8 Weeks
All major organs have begun to form, the umbilical cord is visible, sex organs begin to form, the arms and legs grow longer, fingers and toes begin to form, the eyes have moved forward, eyelids have formed, and the babies heartbeats at he normal rhythm. -
12 Weeks
The eyelids close to protect developing eyes, the nerves and muscles begin to work together, and external sex organs show if the baby is a boy or girl. -
Period: to
Second Trimester
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16 Weeks
Skin begins to form, Meconium develops in the babies intestinal tract, the baby develops a sucking reflex, Muscle tissue and bone continue to form. -
20 Weeks
Eyebrows, fingernails, eyelashes, and toenails have formed, the baby is covered in hair called lanugo and a waxy coating called vernix, the baby can hear and swallow, and the baby is more active. -
24 Weeks
Footprints and fingerprints have formed as well as taste buds, and hair on the babies head. Bone marrow begins to make blood cells, lungs have formed, but do not work, hand reflex develops, and the baby sleeps and wakes regularly. -
Period: to
Third Trimester
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32 Weeks
Lanugo begins to fall off, lungs are not fully formed but practice breathing motions, the eye open and close and sense changes in light, the baby's bones are formed, but are still soft, and the baby's kicks are forceful. The baby begins to store vital minerals, such as calcium and iron. -
36 Weeks
Body fat increases, movements are less forceful, and vernix becomes thicker. -
Week 37
The baby is considered full term. The baby's organs are ready to function on their own, the baby may turn into a head-down position for birth.
