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Chapter 3 - 03:12 Chapter 3 Prenatal Development What are...

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03:12 Chapter 3: Prenatal Development What are the three periods of prenatal development and what happens during each? 1. Germinal [0-2 weeks] o cells divide and differentiate, placenta forms (oxygen/nutrients are transferred, waste is removed), zygote attaches to uterine wall 50% fail to implant 2 . Embryonic [3-8 weeks] o zygote is now called embryo, cells differentiate into key body systems o 2 types of prenatal development in embryonic: cephalocaudal: top to bottom; head to toe proximodistal: inner to outer; torso to extremities 3. Fetal [9-38 weeks] o embryo becomes fetus, major body parts are grown and become redefined, 12 weeks: move arms & legs, 20 weeks: gender is known, 22 weeks: age of viability (can survive independently outside of mother), 24 weeks: baby turns upside down What are teratogens? When are they more likely to cause major developmental abnormalities? When are women “in the clear” from the harmful effects of teratogens? Teratogens : Substances in the environment that can cause harm to the baby (abnormalities) during prenatal development o greatest danger during embryonic period o i.e.: drugs, alcohol, stress, pollution, food, etc. o (always harmful) Least impact in germinal period until child birth What options do pregnant women have to test the fetus for developmental abnormalities during pregnancy?
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1. Ultrasound : produces computer image of the fetus, most common, least harmful/evasive 2. Amniocentesis : withdraw amniotic fluid via needle inserted through mom’s stomach 3. Chrolonic Villus Sampling (CVS) : cells are sanctioned from the placenta through vagina; high risk of miscarriage 4. Genetic Counseling : explore family histories of genetic disorders o ~10% of babies will be born with some type of developmental disorder What happens during each stage of labor? Stage 1. Cervix continues to dilate, regular contractions (longest period) Stage 2. Baby’s head crowns, baby is delivered (between 30 min- 3 hrs) Stage 3. Placenta is expelled o Emotional bonding should start within first 12 hrs after birth How do anoxia, low birth weight, and premature birth affect babies’ development?
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