Teratology and Hazards of Prenatal Development
▪ A teratogen is any agent that causes a birth defect. The word comes from the Greek word ter
meaning “monster.” The field of study that investigates the causes of birth defects is called
teratology.
▪ Teratogens include drugs, incompatible blood types, environmental pollutants, infectious
diseases, nutritional deficiencies, maternal stress, and advanced maternal and paternal age.
• Practically every fetus is exposed to at least some teratogens as many teratogens exist . For th
reason, it is difficult to determine which teratogen causes which defect. It may take a long tim
for the effects of a teratogen to show up. Some of potential effects appear at birth.
• The dose, genetic susceptibility, and the time of exposure to a particular teratogen influence
severity of the damage to an unborn child and the type of defect:
▪ Dose:
• The severity of the teratogen’s effect is directly related to the amount (dose) of exposure.
• A higher dose usually leads to more significant damage.
, Genetic Susceptibility:
• The effect of a teratogen depends on genetic factors:
• The mother’s genotype and the genotype of the embryo/fetus can both play a role. For exam
how a mother metabolizes a drug influences how much of it reaches the fetus.
• Some fetuses may be genetically more vulnerable to specific teratogens.
• Research also shows that male fetuses tend to be more susceptible than female fetuses, thou
the reason is not fully understood.
Time of Exposure:
• Teratogens are most dangerous at certain stages of development:
▪ A teratogen is any agent that causes a birth defect. The word comes from the Greek word ter
meaning “monster.” The field of study that investigates the causes of birth defects is called
teratology.
▪ Teratogens include drugs, incompatible blood types, environmental pollutants, infectious
diseases, nutritional deficiencies, maternal stress, and advanced maternal and paternal age.
• Practically every fetus is exposed to at least some teratogens as many teratogens exist . For th
reason, it is difficult to determine which teratogen causes which defect. It may take a long tim
for the effects of a teratogen to show up. Some of potential effects appear at birth.
• The dose, genetic susceptibility, and the time of exposure to a particular teratogen influence
severity of the damage to an unborn child and the type of defect:
▪ Dose:
• The severity of the teratogen’s effect is directly related to the amount (dose) of exposure.
• A higher dose usually leads to more significant damage.
, Genetic Susceptibility:
• The effect of a teratogen depends on genetic factors:
• The mother’s genotype and the genotype of the embryo/fetus can both play a role. For exam
how a mother metabolizes a drug influences how much of it reaches the fetus.
• Some fetuses may be genetically more vulnerable to specific teratogens.
• Research also shows that male fetuses tend to be more susceptible than female fetuses, thou
the reason is not fully understood.
Time of Exposure:
• Teratogens are most dangerous at certain stages of development:
