Fetal development - Weeks 9 to 38
Weeks 9-12 • Fetal development during the third month includes: • A large head, about 1/2 the length of the fetus. • Visible eyes and ears. • A detectable heartbeat. • Kidneys that form urine. • Gender identification. • Weak, undetectable body movements. • By the end of the twelfth week after fertilization, the placenta is exchanging nutrients and producing essential hormones. Weeks 13-16 • In the fourth month of fetal development, the face looks more human as the eyes and ears move to their final positions • Organ Systems continue to rapidly develop. • The gender is usually easily determined now. • The fetus grows to a length of about 6 or 7 inches and weighs about 4 ounces. Weeks 17-38 • By the end of the fifth month of development: • The fetus grows to weigh about one pound. • Fetal movements become perceptible. • Fine hair called lanugo forms over the fetus. • The head becomes less disproportionate as limbs and trunk grow. • During the seventh month : • The fetus increases in weight to 2 to 3 pounds as it gains body fat. • Testes begin to descend. • Many infants born prematurely at this time do survive with intensive medical support. • In the ninth month: • Much of the fine lanugo hair is shed. • The brain continues to develop. • The fetus now weighs 7 to 8 pounds and is about 20 inches long. • About a quart of amniotic fluid surrounds and protects the fetus. • In the span of only 9 months, a fertilized oocyte develops from a single cell into a mature 8-pound fetus, ready to leave the womb and begin life on its own.
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