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28 Cards in this Set

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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)

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)

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)

Teratogens

- Agents that cause malformations


- Causative agents can include infectious agents (rubella, etc), physical agents (radiation, etc), drugs, environmental chemicals, maternal health factors

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

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

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

Congenital Disorders caused by Genetic Mutations

- Autosomal Dominant; Achondroplasia, Apert's Syndrome


- Autosomal Recessive; Sickle Cell Anemia, Limb Deformities


- X-Linked Recessive; Hemophilia

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


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


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

Thelidomide

- Highly teratogenic during 25-50 days


- Inhibits angiogenesis (development of blood vessels)


- Malformations of limbs, facial and systemic abnormalities


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

Mercury Contamination

- Bioaccumulation in food chain


- Prenatal most affected


- Mental retardation, cerebral palsy, blindness, CNS impairments


Anticonvulsants

- Control seizure disorders


- Neural, facial and liver abnormalities


- Fetal Valproate Syndrome (dysmorphic faces, impaired intellectual development & increased autism)


Alcohol as a Teratogen

- Fetal Alcohol Syndrome


- Growth deficiency, facial dysmorphogenesis, CNS effects (brain structure, behaviour)


- Leading cause of mental retardation

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

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

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

Screening Prenatally for Birth Defects

- Identify higher risk individuals


- Diagnostic test (invasive) looks at particular individuals


- Looking for: Birth defect (NTD), aneuploidy, mutations

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)

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


Diagnostic Tests

- Risk of miscarriage


- Invasive


- Only recommended if something wrong with screening test, family history or advanced maternal age


- Screen for chromosomal abnormalities

Amniocentesis

Screening amniotic fluid for abnormalities

Chorionic Villus Sampling

Test in early pregnancy to detect congenital abnormalities in the fetus


- Sample taken from villi of the chorion which forms placenta

What to do if an anomaly is detached?

- Complete pregnancy and take precautions at birth


- Terminate pregnancy


- Fetal surgery


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

Fetal Mylomeningocele (i.e. ?) Surgery

- I.e., Spina Bifida


- Repair