What Is the Baby's Development In the Third Trimester?
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Weeks 28 to 30
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The third trimester begins in the twenty-eighth week of pregnancy, which is 26 weeks following conception. This marks the point after which the baby has a 90 percent survival chance if delivered premature. During these first three weeks of the trimester, the baby's eyes begin to open, the bones complete formation, and weight and inches are gained. By the thirtieth week, the eyes are completely open with the eyelashes fully formed and most babies are about 10 1/2 inches, having grown 1/2 inch over the last three weeks.
Weeks 31 to 33
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By the thirty-first week--29 weeks after conception--the baby's sexual organs are visible and developed. Movement and kicking can become stronger, and the languno coating of fine hair falls off. The baby will also now respond to external light stimuli. This is a result of the ability of the pupils in the eyes to contract in the presence of bright light. By the thirty-third week, the baby has added another 1/2 inch in height and weights approximately 3-1/2 lbs.
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Weeks 34 to 36
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The thirty-fourth week begins a period of rapid growth. Within a week, the baby will grow nearly 1 inch, and starting with the thirty-sixth week, he will gain 1/2 lb. weekly until birth. With such rapid growth, kicking inside the womb subsides and is replaced with shifting and moving.
Weeks 37 to Delivery
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The baby comes to full term at 37 weeks. A shift in his position points his head downward, and the organs are fully capable of functioning outside of the womb. During the thirty-eighth week, the toenails reach the tips of the toes and the baby can grip with his hands. With the thirty-ninth week, the sexual organs complete the formation with testes descending in boys and the labia majora develop in girls. The baby also has the ability to control body temperature better through an ample layer of "baby fat" in the body. The placenta starts the manufacture of antibodies in preparation for birth. By the fortieth week--38 weeks after conception--delivery is imminent.
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References
- Photo Credit Wikicommons: http://commons.wikimedia.org/wiki/File:Color40_weeks_pregnant.jpg
