PSY 220 - Chapter 2.5
fetal alcohol syndrome (FAS)
a cluster of defects appearing after heavy prenatal exposure to alcohol that is detected in 2 to 7 infants per 1,000 births. At the extreme end of the spectrum.
Teratogen
an agent that causes damage to prenatal development, such as a disease, drug, or other environmental factor, producing a birth defect.
spina bifida
occurs when the lower part of the neural tube fails to close and spinal nerves begin to grow outside of the vertebrae, often resulting in paralysis. Surgery must be performed before or shortly after birth, but lost capacities cannot be restored.
Anencephaly
occurs when the top part of the neural tube fails to close and all or part of the brain fails to develop, resulting in death shortly after birth.
Dose
The amount of exposure (i.e., dosage) to a teratogen influences its effects. Generally, the greater the dose, the more damage to development; however, teratogens also differ in their strength. Some teratogens, like alcohol, display a powerful dose-response relationship so that larger doses—heavier and more frequent drinking—result in greater damage.
Teratogens show complicated effects on development
Different teratogens can cause the same birth defect, and a variety of birth defects can result from the same teratogen. Also, some teratogens have subtle effects that result in developmental delays that are not obvious at birth. For example, infants exposed prenatally to as little as an ounce of alcohol a day usually display no obvious physical deformities, but later, as children, they may demonstrate cognitive delays. Other teratogens display sleeper effects—effects that are not visible until many years later. For example, infants born to women who consumed diethylstilbestrol (DES), a hormone that was widely prescribed between 1945 and 1970 to prevent miscarriages, were born healthy, but as adults they were more likely to experience problems with their reproductive systems. Daughters born to mothers who took DES were more likely to develop a rare form of cervical cancer, have miscarriages, and give birth to infants who were premature or low birth weight.
individual differences
Individuals vary in their susceptibility to particular teratogens based on the genetic makeup of both the organism and mother, as well as the quality of the prenatal environment.
Critical periods
There are critical periods during prenatal development in which an embryo is more susceptible to damage from exposure to teratogens. The extent to which exposure to a teratogen disrupts prenatal development depends on the stage of prenatal development when exposure occurs. Generally, sensitivity to teratogens begins at about 3 weeks after conception. Structural defects occur when the embryo is exposed to teratogen while that part of the body is developing. each organ of the body has a sensitive period in development during which it is most susceptible to damage from teratogens. Once a body part is fully formed, it is less likely to be harmed by exposure to teratogens; however, some body parts, like the brain, remain vulnerable throughout pregnancy.
fetal alcohol spectrum disorders
refer to the continuum of effects of exposure to alcohol, which vary with the timing and amount of exposure.