Teratogenesis Flashcards
What is teratogenesis?
the process by which congenital malformations are produced in an embryo or fetus
What are the five principles of teratogenesis?
-Susceptibility to teratogens is variable
-susceptibility is specific for stage of development of embryo or fetus
-the mechanism of teratogenesisis specific for each teratogen
-teratogenesis is dose-dependent
-teratogens produce death, growth, retardation, malformation, or functional impairment
Approximately 31% of fertilizations end in what?
spontaneous abortions
About 3% of infants are born with what?
structural anomalies
What is the critical fetal period for teratogenesis and why?
3-16 weeks due to impairment of organogenesis
What are the potential adverse effect(s) of fetotoxic exposure at pre-implantation stage?
spontaneous abortions
What are the potential adverse effect(s) of fetotoxic exposure at the embryonic (2-8 weeks) stage?
-spontaneous abortions
-structural malformations
What are the potential adverse effect(s) of fetotoxic exposure at the fetal (8-40 weeks) stage?
-central nervous system function
-growth restriction
-neurobehavioral effects
-fetal demise
When do most birth defects occur and why is this an issue?
occur prior to 8 weeks which is usually before the first prenatal appointment
What should you do whenever you are prescribing medications to a patient who is of child-bearing age?
ensure you know the pregnancy status by asking when their last menstrual period was and if they could be pregnant
What is the description of category A medications?
well-controlled studies in humans show no risk to the fetus
What is the description of category B medications?
no well-controlled studies have been conducted in humans; animal studies show no risk to the fetus
What is the description of category C medications?
no well-controlled studies have been conducted in humans; animal studies have demonstrated an adverse effect on the fetus
What is the description of category D medications?
evidence of human risk to the fetus exists; however, benefits may outweigh risks in certain situations
What is the description of category X medications?
controlled studies in animals or humans demonstrate fetal abnormalities; the risk in pregnant women clearly outweighs any possible benefit
Drugs in the mother’s blood can pass through what structure to get to the fetus?
the umbilical cord
What was a medication marketed in the 1950s for nausea in pregnancy and was widely used in Europe, Australia, and Japan?
thalidomide
Why was approval of the use of thalidomide in the US withheld?
Dr. Frances Kelsey was concerned over the safety and side effects of thalidomide such as peripheral neuropathy
What is peripheral neuropathy?
weakness, numbness, and pain in your extremities
What did the tragedy of thalidomide lead to?
the development of testing of pharmaceuticals for adverse effects on fetal development
What are these deformities associated with?
-amelia
-meromelia
-phocomelia
thalidomine use
What is amelia?
complete absence of a limb or limbs
What is meromelia?
partial absence of a limb
What is phocomelia?
form of meromelia where there is an absence of long bones with hands and feet attached to trunk with small rudimentary bones