THE CRITICAL PERIODS AND TERATOGENICS
Critical Periods <ul><li>The critical periods are times during which certain environmental influences can have an impact o...
Definition of Teratogenics <ul><li>Any agent that causes a birth defect (from the Greek word  teras  meaning ‘monster’) </...
The Thalidomide Disaster <ul><li>Early 1960s </li></ul><ul><li>Prescribed as sedative to control nausea </li></ul><ul><li>...
Effects of teratogenic agents on prenatal development <ul><li>1) Sensitive periods:   </li></ul><ul><li>Varies with organ ...
<ul><li>2)  Tissue-specific effect </li></ul><ul><li>Each teratogen acts in a specific way on specific developing tissue  ...
<ul><li>3) Dose-response relationship </li></ul><ul><li>* > concentration of teratogenic = > risk of abnormal development ...
<ul><li>4) Individual differences in effect </li></ul><ul><li>Response depends to some degree on its genotype and that of ...
Influences and Effects <ul><li>Malnutrition </li></ul><ul><li>Drug and alcohol intake </li></ul><ul><li>Illnesses </li></u...
Malnutrition <ul><li>Higher chance of premature or low-birthweight infants </li></ul><ul><li>Affects developing brain – ca...
Drug Intake <ul><li>Drugs can cross the placenta </li></ul><ul><li>Strongest effect in early pregnancy </li></ul><ul><li>I...
Drug Effects  Aspirin Increased risk of bleeding for mother and baby; harm to circulatory system Oral contraceptives  Incr...
Illnesses <ul><li>Disease producing organisms in the mother’s blood can sometiems infect the foetus via the placenta </li>...
External Environmental Hazards <ul><li>Radiation – gene mutations, higher incidence of cancers, physical deformities </li>...
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04 teratogenics

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04 teratogenics

  1. 1. THE CRITICAL PERIODS AND TERATOGENICS
  2. 2. Critical Periods <ul><li>The critical periods are times during which certain environmental influences can have an impact on the development of a child. </li></ul><ul><li>The most likely time for a miscarriage, or spontaneous abortion, is in the first three months, as the organs are forming and first becoming functional. </li></ul><ul><li>15-20% end in miscarriage </li></ul>
  3. 3. Definition of Teratogenics <ul><li>Any agent that causes a birth defect (from the Greek word teras meaning ‘monster’) </li></ul><ul><li>Includes drugs, chemicals, viruses – any substance or factor that can cause a defect. </li></ul>
  4. 4. The Thalidomide Disaster <ul><li>Early 1960s </li></ul><ul><li>Prescribed as sedative to control nausea </li></ul><ul><li>4 th -6 th weeks – abnormalities. </li></ul><ul><li>Fused fingers and toes, dislocated hips, missing limbs, hands and feet attached to torso, facial malfunctions, malformed organs. </li></ul><ul><li>10, 000 children worldwide before detection. </li></ul>
  5. 5. Effects of teratogenic agents on prenatal development <ul><li>1) Sensitive periods: </li></ul><ul><li>Varies with organ systems developing at different times. </li></ul><ul><li>Germinal period - zygote may be completely destroyed. </li></ul><ul><li>Embryonic period –most vulnerable in structural abnormality </li></ul><ul><li>Foetal period – more likely function than structure. </li></ul>
  6. 6. <ul><li>2) Tissue-specific effect </li></ul><ul><li>Each teratogen acts in a specific way on specific developing tissue </li></ul><ul><li>E.g. thalidomide – limb deformation, while mercury causes brain damage. </li></ul>
  7. 7. <ul><li>3) Dose-response relationship </li></ul><ul><li>* > concentration of teratogenic = > risk of abnormal development </li></ul>
  8. 8. <ul><li>4) Individual differences in effect </li></ul><ul><li>Response depends to some degree on its genotype and that of its mother. </li></ul><ul><li>Mother’s age, nutrition, hormonal balance can all affect the action of teratogens </li></ul>
  9. 9. Influences and Effects <ul><li>Malnutrition </li></ul><ul><li>Drug and alcohol intake </li></ul><ul><li>Illnesses </li></ul><ul><li>External environmental hazards </li></ul>
  10. 10. Malnutrition <ul><li>Higher chance of premature or low-birthweight infants </li></ul><ul><li>Affects developing brain – can contain as few as 60% of normal number of cells </li></ul><ul><li>Major concern for low socio-economic families </li></ul>
  11. 11. Drug Intake <ul><li>Drugs can cross the placenta </li></ul><ul><li>Strongest effect in early pregnancy </li></ul><ul><li>Ideally no medication should be prescribed for pregnant or breastfeeding women unless it is absolutely essential for her health or that of her child. </li></ul>
  12. 12. Drug Effects Aspirin Increased risk of bleeding for mother and baby; harm to circulatory system Oral contraceptives Increased risk of birth defects Marijuana Irritability, nervousness, tremors; easily disturbed, startles Alcohol Foetal alcohol syndrome (FAS) – mental retardation, delayed growth, facial malformation; learning difficulties, smaller head Opiates Likely to bear premature babies addicted to the drugs in the womb Nicotine Miscarriage, low birth weight, stillbirth, short stature, mental retardation, learning disabilities Caffeine Miscarriage, low birth weight Cocaine Decreased height, low birth weight, respiratory problems, seizures, learning difficulties; addiction
  13. 13. Illnesses <ul><li>Disease producing organisms in the mother’s blood can sometiems infect the foetus via the placenta </li></ul><ul><li>Minor effects on the mother can still have serious effects on the foetus. </li></ul><ul><li>E.g. rubella can cause blindness, deafness or heart disease in the foetus in first four weeks of pregnancy </li></ul><ul><li>Other diseases that can be transmitted include: chicken pox, mumps, malaria, syphilis, herpes and AIDS. </li></ul>
  14. 14. External Environmental Hazards <ul><li>Radiation – gene mutations, higher incidence of cancers, physical deformities </li></ul><ul><li>High temperatures – increased chance of neural tube defects, such as spinal bifida </li></ul>

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