Age of viability: 23-25 weeks What is a critical period, teratogen? Critical period : an optimal period for development of specific physical or cognitive capabilities o Exposure to certain environmental stimuli or experiences influences development o Impact can be positive or negative o The effects of a teratogenic agent are worst during the critical period when an organ system grows most rapidly Teratogen: any disease, drug, or other environmental agent that can harm a developing fetus o Agents (chemical, viral) that reaches the fetus during prenatal development and cause harm o Effects of a teratogen depends when exposure occurred: when o Not all embryo/fetuses are affected equally: genetic susceptibility o Higher/longer the exposure, the greater the damage: dose o Different teratogens may cause the same effect: what o The same teratogen may cause different effects, depending on timing: timing of exposure Drugs: alcohol, FAS, nicotine, cocaine, thalidomide. Alcohol: causes overshoot of neuron migration o FAS (fetal alcohol syndrome): child has the behaviors and facial features o FES (fetal effect syndrome): child has some behaviors and facial features, but not all Nicotine: low birth weight, high risk birth Cocaine: low birth weight, cognitive deficits Thalidomide: the child will have missing or flipper arms o Originally taken for nausea 15
Infectious diseases: rubella, syphilis (know specific effects at specific times), HIV. Rubella: german measles o Most dangerous during the first 3 months (first trimester) o 0-8 weeks (zygote and embryo period): 60% - 80% chance of damage to nervous system, eyes, and heart o 6-13 weeks: 50% chance of deafness Syphilis: vaginal disease that occurs in three stages: 1. On vagina 2. In the blood 3. Effects different organs o Most damaging in the middle to late stages o Blindness, deafness, brain damage, heart problems HIV: sexual disease o Damaging all throughout pregnancy and can be during and after birth o Transmitted: prenatally through the placenta, during birth, and breast feeding o Body fluids that transmit it: blood, vaginal secretion, semen, breast milk o Signs that the baby has it: compromised immune function Environmental hazards: radiation Stops neuron migration short of where they are supposed to go. Low-birth weight infants, folic acid. Anoxia, delivery complications, medications, APGAR . Low- birth weight babies: at risk babies. The younger and smaller the baby is a birth, the lower their chance of survival. Folic acid: a lack of this is very bad o Found in: leafy greens, orange juice, enriched grains o Needed for: production, repair, and function of DNA o Without it: neural tube defects, miscarriage, cleft lip, limb defects, heart defects,
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- Spring '08