1Hazards to Prenatal Development:Teratogens• Teratogens are any agents from the environment thatcan cause harm to the developing fetus.• Many harmful agents cause damage only if exposureoccurs during a sensitive period of prenataldevelopment.• Critical factors that influence the degree of harm ateratogen will cause:– The amount and length of exposure– Individual differences in susceptibility• The impact of a teratogen depends on the genotype ofthe organism. (e.g. thalidomide, alcohol)• The impact of teratogens changes of the course ofprenatal development.• Each teratogen affects a specific aspect (or aspects) ofprenatal development. (e.g. PCBs)• Impact of teratogens depends on the dosage.• Damage from teratogens is not always evident at birthbut may appear later in life. (e.g. DES)• Impact of teratogens often depends on quality ofpostnatal environment2Hazards to Prenatal Development:Miscarriage• About 45% or more pregnancies end in miscarriage,that is, spontaneous abortion.• Most miscarried fetuses have severe defects, such asmissing chromosomes, that make further developmentimpossible.• Ninety percent of fetuses that survive the danger ofmiscarriage are born normal.Risk Factors• Age• Nutrition• Exercise• Stress3Risk Factors• Age– Pregnancy most likely to result in a healthybaby if mother is in her 20’s.– Older mothers have increased risk ofmiscarriage and stillbirth and are more liable togive birth to Down syndrome children.– Younger mother are at greater risk forinadequate diets and prenatal care and are morelikely to have children with behavioralproblems.Risk Factors• Age• Nutrition– Malnourished newborns have smaller braincells and are more vulnerable to illnesses thanwell-nourished newborns.– Malnutrition in early prenatal development maylead to serious physical defects (e.g. folic acid)– Malnutrition in the last few months may lead tolow birth weight and small heads.4Risk Factors• Age• Nutrition• Exercise– Regular, moderate exercise is related toincreased birth weight.– Frequent, vigorous exercise predicts lower birthweight.Risk Factors• Age• Nutrition• Exercise• Stress– In animals, stress results in smaller offspring prone tobehavioral problems.– In humans, extreme maternal stress may be related tolower birth weight and children with emotionalproblems and behavioral disorders.5DNAalcoholnutritionstresshormonesactivityThe case of low birth weight• Low birth weight is associated with:– Caffeine, smoking, marijuana– Stress, inadequate nutrition– Premature birth– “difficult” temperament– Lagging cognitive development– Unstable families– Lagging social development– Behavioral problemsWhich are causes?Which are
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