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.
• • • • Age Nutrition Exercise Stress
– Pregnancy most likely to result in a healthy baby if mother is in her 20’s. – Older mothers have increased risk of miscarriage and stillbirth and are more liable to give birth to Down syndrome children. – Younger mother are at greater risk for inadequate diets and prenatal care and are more likely to have children with behavioral problems.
• Age • Nutrition
– Malnourished newborns have smaller brain cells and are more vulnerable to illnesses than well-nourished newborns. – Malnutrition in early prenatal development may lead to serious physical defects (e.g. folic acid) – Malnutrition in the last few months may lead to low birth weight and small heads....