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28 Cards in this Set
- Front
- Back
History; What is teratology? Rubella Virus? Fraser Group? Thalidomide? |
- Teratology is the "study of monsters"; study of congenital malformations - Rubella virus caused syndrome of abnormal development - Fraser group MTL; Cortisone effects on cleft palate in mice varied with strain (teratogenetics) - Thalidomide; A sedative used widely in Germany, linked to phocomelia and amelia (missing limb) |
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Developmental Disorders |
Malformations can happen in many ways: - heart defects - incomplete closure of neural tube - failure of fusion to form lips (cleft lip) - failure of palatal shelves to meet midline and fuse (cleft palate) |
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Malformations Cont'd |
- Missing limbs; phocomelia, amelia - Improper placement of urethral opening in penis (hypospadia) - Failure of tissues between toes to break down (syndactyly) - Extra fingers and toes (polydactyly) |
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Teratogens |
- Agents that cause malformations - Causative agents can include infectious agents (rubella, etc), physical agents (radiation, etc), drugs, environmental chemicals, maternal health factors |
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Studies identifying associations between teratogens and birth defects |
- Study of distributions/risk factors of diseases in a population - Studies that measure associations but not causality - Two types: Cohort & Case Study |
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Measurements of Disease Frequency |
- Prevalence: Measure of disease state (the # of people with x at a given time over the population at risk) - Incidence: The measure of speed at which new causes of diseases (or deaths) arise in a population over a given time |
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Congenital Heart Defects |
- Most common birth defect - Can often hear heart murmur - Defects can involve: Interior walls of the heart, valves inside heart, arteries and veins - Causes (many unknown): Premature birth, genetic defects, viral infection from mother, drugs, alcohol, OTC medication - Aneuploidy or Structural Errors |
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Congenital Disorders caused by Genetic Mutations |
- Autosomal Dominant; Achondroplasia, Apert's Syndrome - Autosomal Recessive; Sickle Cell Anemia, Limb Deformities - X-Linked Recessive; Hemophilia |
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Principles of Teratology |
- The capacity of an agent to produce birth defects is influenced by: • Developmental stage at time of exposure • Dose and duration of exposure • Genotype of embryo • Mechanisms of action
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Critical Periods of Susceptibility |
- First 3 weeks unlikely to lead to deficits (either death or compensation) - Maximal susceptibility between 3-8 weeks (most organ development) - Anomalies from 3-9 months; Disturbances in growth of already formed parts
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Rubella |
- Respiratory disease caused by virus - Mild measles; Rash & Fever - Congenital Rubella Syndrome (CRS) • Cardiovascular defects, skin rash, mental retardation, deafness, small eyes & head, liver and spleen damage |
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Thelidomide |
- Highly teratogenic during 25-50 days - Inhibits angiogenesis (development of blood vessels) - Malformations of limbs, facial and systemic abnormalities
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Prenatal Exposures (long-term effects on brain and behaviour) |
- Vulnerable from 1st trimester to adolescence - Neurotoxic effects subtle - Mercury & Heavy Metals - Prescription drugs - Recreational drugs - Illegal drugs |
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Mercury Contamination |
- Bioaccumulation in food chain - Prenatal most affected - Mental retardation, cerebral palsy, blindness, CNS impairments
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Anticonvulsants |
- Control seizure disorders - Neural, facial and liver abnormalities - Fetal Valproate Syndrome (dysmorphic faces, impaired intellectual development & increased autism)
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Alcohol as a Teratogen |
- Fetal Alcohol Syndrome - Growth deficiency, facial dysmorphogenesis, CNS effects (brain structure, behaviour) - Leading cause of mental retardation |
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Illegal Drugs |
- Easily cross the placenta and some (methamphetamine) accumulate more in the fetus - No obvious congenital malformations - Animal studies with cocaine --> Dopamine alteration (attention) - Methamphetamine; changes in brain structure, neurotransmitters, spatial memory and language development |
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Maternal Pre-Existing Diabetes |
- Uncontrolled blood sugar - Leads to birth defects (heart, brain, spinal cord) - Stillbirth or miscarriage - Large baby - Low blood sugar after birth - Increase chance of obesity |
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Nutritional Deficiencies |
- Extreme calorie restriction; premature & very low birth weights - Iodine deficiency; death, growth restriction, deformed & mentally handicapped - Vitamin B; NTD - Vitamin A; blind, expression of genes alteration |
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Screening Prenatally for Birth Defects |
- Identify higher risk individuals - Diagnostic test (invasive) looks at particular individuals - Looking for: Birth defect (NTD), aneuploidy, mutations |
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Ultrasound |
- Sound-wave reflections to make images - 1st scan in 1st trimester (confirm gestational age and # of fetuses, nuchal translucency is screening for aneuploidy by measuring thickness of fluid compartment in neck) - 2nd scan in 2nd trimester (identify half of structural malformations) |
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Maternal Serum Alpha-Fetoprotein (AFP) |
- secreted by fetal liver excreted in urine - Crosses placenta - High levels due to open NTD, abdominal wall defect, abnormal maternal-placental interface, inaccurate gestational age - Triple Screen measures other molecules such as hCG and estriol; Low APF, abnormal hCG and estriol can lead to aneuploidy
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Diagnostic Tests |
- Risk of miscarriage - Invasive - Only recommended if something wrong with screening test, family history or advanced maternal age - Screen for chromosomal abnormalities |
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Amniocentesis |
Screening amniotic fluid for abnormalities |
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Chorionic Villus Sampling |
Test in early pregnancy to detect congenital abnormalities in the fetus - Sample taken from villi of the chorion which forms placenta |
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What to do if an anomaly is detached? |
- Complete pregnancy and take precautions at birth - Terminate pregnancy - Fetal surgery
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Fetal Heart Surgery |
- Hypoplastic left heart syndrome - Blockage of aortic valve prevents growth of left ventricle - Fatal if untreated - Fetal operation may allow child to be born with healthy heart |
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Fetal Mylomeningocele (i.e. ?) Surgery |
- I.e., Spina Bifida - Repair
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