How do minor anomalies help in diagnosis of major abnormalities?
If 1 is present there is a 3% chance a major is present, if 2 are present then 10% chance and if 3 are present 20% chance.
What determines the susceptibility of the conceptus to teratogens?
Fetal genotype + maternal genotype.
How does susceptibility to teratogens vary by age?
Most susceptible from weeks 0-3: high w/exposure = death. Weeks 3-8: exposure = organ failure. Weeks 8-on: less defects.
What viruses are teratogens?
Rubella, CMV and HSV.
What happens to the fetus when the mother is infected by rubella virus?
All fetal cells are infected by rubella virus and cataracts, glaucoma, heart defects, deafness and tooth abnormalities present in 50-90% of fetuses. Note that the number of affected fetuses declines through the second trimester
Ways to prevent congenital rubella syndrome
Vaccinate the mother.
Aside from viral infection and viral damage, how is infection teratogenic?
Elevated body temperature is teratogenic.
What physical agents are teratogens?
Hyperthermia and x-rays.
What chemical agents are teratogens?
What was thalidomide used for? What defect do you see with its use?
Morning sickness. This drug was prescribed at a time when the fetus is highly susceptible to teratogens (3-8) weeks because that is when mom gets sick. Defect - phocomelia (defect in formations of the long bones of the limb)
A mother has a child with a depressed nasal ridge, short nose, flat mid face, indistinct philtrum and thin upper lip. She is also mentally retarded. What teratogen could have caused this?
Alcohol, the leading cause of mental retardation. Damage to fetus is dose dependent.
What is the most common birth defect seen in oral use of isotretinoin for acne in the third to fifth weeks?
Microcephaly. Hydrocephaly, ear/eye abnormalities, cleft palate, heart defects and spontaneous abortion are also common.
What are the hormonal teratogens and what effects do they have on the fetus?