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Hazards to Prenatal Development:
Teratogens
•Teratogens are any agents from the environment that
can cause harm to the developing fetus.
•Many harmful agents cause damage only if exposure
occurs during a sensitive period of prenatal
development.
•Critical factors that influence the degree of harm a
teratogen will cause:
–The amount and length of exposure
–Individual differences in susceptibility
•The impact of a teratogen depends on the genotype of
the organism. (e.g. thalidomide, alcohol)
•The impact of teratogens changes of the course of
prenatal development.
•Each teratogen affects a specific aspect (or aspects) of
prenatal development. (e.g. PCBs)
•Impact of teratogens depends on the dosage.
•Damage from teratogens is not always evident at birth
but may appear later in life. (e.g. DES)
•Impact of teratogens often depends on quality of
postnatal environment
Hazards to Prenatal Development:
Miscarriage
•About 45% or more pregnancies end in miscarriage,
that is, spontaneous abortion.
•Most miscarried fetuses have severe defects, such as
missing chromosomes, that make further development
impossible.
•Ninety percent of fetuses that survive the danger of
miscarriage are born normal.
Risk Factors
•Age
•Nutrition
•Exercise
• Stress
