Teratogens

 

Teratogens----agents and conditions, including viruses, drugs, chemicals, stressors, and malnutrition, which can impair prenatal development and lead to birth defects or even death

 

Behavioral teratogens---teratogens that tend to harm the prenatal brain, affecting the future childís intellectual and emotional functioning.

à although all teratogens increase the risk of harm to the developing child, none always cause damage; the ultimate impact depends on the complex interplay of many factors

 

Factors influencing the effect of teratogens

  1. Timing---the effect of a teratogen on the developing organism depends on what period in the pregnancy (in development) the child is exposed to the teratogen.
  2. à some teratogens cause damage only during specific days or weeks in early pregnancy

    à other teratogens are harmful at any time during the pregnancy---for example, for behavioral teratogens, there is no safe period---the brain and nervous system can be harmed throughout the pregnancy

     

    critical period---in prenatal development, the time when a particular organ or other body part is most susceptible to teratogenic damage

     

  3. Exposure---the effect of a teratogen on the developing organism also depends on the dose and/or frequency of exposure of/to the teratogen
  4.  

    Threshold effect---the phenomenon in which a particular teratogen is relatively harmless in small doses but becomes harmful when exposure reaches a certain level (the threshold)

     

    Interaction effect---the phenomenon in which a particular teratogenís potential for causing harm increases when it is combined with another teratogen or another risk factor

  5. Genetic variability----another factor that determines whether a specific teratogen will be harmful is the genetic make-up of the developing organism.

à possessing and not possessing certain genes may make the developing child more susceptible to the effect of a teratogen

 

 

Examples of Teratogens

 

A)Diseases (Maternal Illness)

 

1. Rubella---a viral disease, if contracted early during pregnancy, can harm the fetus

à causes blindness, deafness, and damage to the central nervous system

    1. HIV
    2. AIDS

 

B) Drugs (Medications or Social Drugs)

 

Medicinal drugs---these are drugs that remedy problems in a personís body that in some cases have teratogenic effect

à i.e., tetracycline, acne medication, aspirin, antacids, diet pills

 

Psychoactive drugs---drugs that affect how the mind works

à i.e, alcohol, tobacco, marijuana, cocaine, heroine

à all psychoactive drugs slow down fetal growth and increase the risk of premature labor

 

Fetal Alcohol Syndrome (FAS)---a cluster of birth defects, including abnormal facial characteristics, slow physical growth, and retarded mental development

à these birth defects are caused by the motherís drinking excessive quantities of alcohol when pregnant

 

C) Environmental Toxins