Stages of Prenatal Development

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

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