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Weeks 1-2
None -
Baby Week 1-2
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Week 3-4
Conception, zygote turns into blastocyst and
travels down the fallopian tube, rapid cell division begins, and blastocyst implants in uterus lining during week 4 and becomes an embryo -
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Weeks 5-6
Neural tube closes; brain and spinal cord will form, heart, organs, and bones start to form, develop head and trunk, arm and leg limb buds appear, brain begins development, eyes and ears begin to form, heart continues to develop, and beats a regular rhythm, baby is 1/6 inch long -
Baby Week 5-6
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Weeks 7-8
Brain and face shape begin growing, four-chamber heart, lungs begin to form, fingers and toes start to form, ear begins to develop internally, lip and nose have formed, trunk and neck begin to straighten, baby is about ½ inch long, all major organs are formed -
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Week 10
Head is half the size of the baby, all body parts are present, eyes, ears, arms, and legs are identifiable, baby is 1 ¼ inches long -
Baby Week 10
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Week 11
Genitals develop, head is about half of the length of baby, teeth buds form, baby is about 2 inches in length and weighs about 1/3 ounce -
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Week 12
Fingernails grow, face has more defined profile, intestines are in the abdomen, about 2 ½ inches in length and weighs about ½ ounce -
Baby Week 12
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Week 14
Baby’s sex will become apparent, baby can swallow and make urine, baby is about 3 ½ inches in length and weighs about 1 ½ ounces -
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Week 16
Baby is moving but mom cannot feel it, baby is about 4 ½ inches in length and weighs about 4 ounces -
Baby Week 16
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Weeks 18-19
Baby begins to hear, digestive system works, cernix caseosa covers the baby -
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Week 20-21
Regular sleep and wake patterns, all organs and structures formed, breathing movements occur but are underdeveloped, covered in Lanugo, may begin to suck thumb, baby is about 6 1/3 inches in length and weighs about 11 ounces -
Baby Week 20-21
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Week 22
Has nails, fingerprints, eyebrows, lashes, and possibly some hair, more active, heartbeat heard with a stethoscope, lowest limit of viability (survival outside the mother), baby is about 7 ½ inches in length and weighs about 1 pound -
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Week 24
Wrinkly skin, translucent and pinkish red, lung development, regular sleep and wake patterns, baby is about 8 inches in length and weights about 1 1/3 pounds -
Baby Week 24
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Weeks 28-29
Eyes begin to partially open and close, central nervous system directs breathing and body temperature control, lungs are capable of breathing air, baby begins to kick and stretch, baby is about 10 inches in length and weighs about 2 ¼ pounds -
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Weeks 31-32
Finished most major development, rapid weight gain begins, lanugo starts to fall off, baby is about 11 inches in length and weighs about 3 ¾ pounds -
Baby Week 31-32
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Week 34
Continues to grow fingernails and toenails, develop breathing motion, responds to light, skin is pink and smooth, baby is about 12 inches in length and weighs about 4 ½ pounds -
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Weeks 36-37
Takes up most of the amniotic sac, starts to turn head down to prepare for labor, baby is about 13 ½ inches in length and weighs about 6 pounds, will continue to gain about ½ pound a week until delivery -
Baby Week 36-37
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Weeks 38-40
Brain, lungs, and liver still developing, brain will double in size between week 35 & 39, lung development during last few weeks helps with fewer complications after birth, at week 39, baby is considered full term, weight gain helps with temperature control once born