FIRST MONTH:  |
Fertilization occurs
Zygote implants itself in the lining of the uterus
Rapid cell division occurs
Embryonic stage lasts from 2 weeks to 8 weeks
Cells differentiate into three distinct layers:
the ectoderm, the mesoderm, and the endoderm
Nervous system begins to develop
Embryo is 1/2 inch long |
SECOND MONTH: |
Heart and blood vessels form
Head area develops rapidly
Eyes begin to form detail
Internal organs grow, especially the digestive system
Sex organs develop rapidly and sex is distinguished
Arms and legs form and grow
Heart begins to beat faintly
Embryo is 1 inch long and weighs 1/10 ounce |
THIRD MONTH: |
Head growth occurs rapidly
Bone formation begins to form rapidly
The digestive organs begin to function
Arms, legs, and fingers make spontaneous movements
Fetus is 3 inches long and weighs 1 ounce |
FOURTH MONTH: |
Lower parts of the body show rapid growth
Bones are distinct in X rays
Reflex movement becomes more active
Heartbeat detected by physician
Sex organs are fully formed
Fetus is 7 inches long and weighs 5 ounces |
FIFTH MONTH: |
Mother begins to feel reflex movements
A fine, downy fuzz covers the entire body
Vernix (a waxy coating) collects over the body
Ears and nose begin to develop cartilage
Fingernails and toenails begin to appear
Fetus shows hiccups, thumb sucking, and kicking
Fetus is 12 inches long and weight 14 ounces |
SIXTH MONTH: |
Eyes and eyelids fully formed
Fat is developing under the skin
Fetus is 14 inches long and weighs 2 pounds |
SEVENTH MONTH: |
Cerebral cortex of brain develops rapidly
Fetus is 17 inches long and weighs 3 pounds |
EIGHTH MONTH: |
Subcutaneous fat is deposited for later use
Fingernails reach beyond the fingertips
Fetus is 17 inches long and weighs 5 pounds |
NINTH MONTH:  |
Hair covering the entire body is shed
Organ systems function actively
Vernix is present over the entire body
Fetus settles into position for birth
Neonate is 21 inches long and weighs 7 pounds |
