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Download 04-Prenatal Development and Birth
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04-PRENATAL DEVELOPMENT AND BIRTH Prenatal development Pregnancy confirmation • Can not be confirmed by blood or urine tests until the zygote implants in the uterus (about 10 days after conception). Prenatal Development • Germinal - 1st 2 weeks • Embryo – Week 3 to 8 (2 months) • Fetus – Week 9 to birth Germinal period • First 2 weeks • Conception • Zygote • Implantation Embryo • Week 3 – 8 (2 months) • First - “Primitive streak” develops = neural tube = brain & spinal column • 4th. Week • Head takes shape • Early heart begins to pulsate • 5th. Week • Arm & leg buds develop • Webbed fingers and toes develop • 8th. Week • 1 inch long • Has all basic body parts and organs (except sex organs) • Embryo – 4 weeks • Embryo – 5 Weeks • Embryo – 7 weeks • Embryo – 8 Weeks Fetus (9 weeks – Birth) 9th. Week • Male gene triggers development of male organs • If not, female organs develop Fourth, fifth, sixth months • Heartbeat becomes stronger • Digestive and excretory systems develop • New neurons & synapses develop • Up to one 500,000 brain cells per minute are created • Age of viability • Can possibly survive outside the mother (with intensive medical care) • 22 weeks Fetus (9 weeks - birth) • Final three months • Lungs begin to expand and contract (fetal respiration) • Breathe using amniotic fluid as a substitute for air • Fetus • Grows and moves more • Startles and kicks at a loud noise • Becomes used to mother’s heartbeat and voice • Responds if mother is fearful or anxious Birth • Labor • 12 hrs. – first child • Stages of labor • 1st. = Cervical dilation • 2nd. = Crowning • About 31% of zygotes survive to be born • Birth in U.S. • Birth in Peru • Birthing chair - Egypt Apgar Scale • Color • Heart • Reflex • Muscle • Breathing (Respiration) • Done twice – 1 & 5 minutes after birth to determine if immediate medical care is needed • Score = 0,1,2 for each item • Total of 7 or above is desired Problems and Solutions Teratogens: (Items increasing prenatal abnormalities) • Types • Substances (drugs, pollution) • Conditions (Stress or malnutrition) • Teratogens = Physical defects • Cleft palate • Thalidomide babies (deformed limbs) Behavioral teratogens = Behavioral defects • Hyperactivity • Antisocial • Learning-disabled Teratogens: Critical factors • Timing • Some only cause damage during critical periods • When organ or body part is most vulnerable • Before pregnancy • Avoid drugs (e.g. alcohol) • Fetal alcohol syndrome • Better diet • Immunizations • Problem – Half of births are unplanned • Threshold effect • Some are harmless until they “cross the threshold” and become harmful • Alcohol, tobacco, and marijuana do more harm in combination • This lowers the threshold for each • Genes – May increase birth defects Low birth weight • Causes • Born preterm • Born small for gestational age (SGA) • Maternal or fetal illness • Drug use • Every psychoactive drug • Tobacco (Most prevalent cause) • Malnutrition • Consequences • Infant death • Thinking (cognitive) problems • Seeing and hearing problems • In adulthood - higher rates of: • Obesity • Heart disease • Diabetes Newborn reflexes • Reflex = involuntary response to a stimulus • Reflexes that aid survival • Breathing – Maintains oxygen • Shivering – Maintains temperature • Sucking – Manages feeding • Rooting – Searching for a nipple • Reflexes that show the state of brain and body functions • Babinski reflex – Toes fan upward when feet are stroked • Stepping reflex • Swimming reflex • Palmer grasping reflex • Moro reflex - Being startled • Sucking reflex • Grasping reflex • Stepping reflex
