Читать книгу Lifespan Development - Tara L. Kuther - Страница 161

There are many ways in which teratogens may affect prenatal development, but it is not always easy to predict the harm caused by teratogens. Generally, the effects of exposure to teratogens on prenatal development vary depending on the following principles (K. S. Moore & Persaud, 2016; Sadler, 2015).

 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 (Webster et al., 2018). Structural defects occur when the embryo is exposed to a teratogen while that part of the body is developing. As shown in Figure 3.6, each organ of the body has a sensitive period in development during which it is most susceptible to damage from teratogens such as drugs, alcohol, and environmental contaminants. 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.

 Dose. The amount of exposure (i.e., dose level) 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, or heavier and more frequent drinking, result in greater damage (Muggli et al., 2017).

 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.

 Complicated Effects. 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 may display no obvious physical deformities at birth but later, as children, may demonstrate cognitive delays (Charness, Riley, & Sowell, 2016). 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 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 birthweight (Conlon, 2017).

Description

Figure 3.6 Sensitive Periods in Prenatal Development

Source: Levine and Munsch (2010, p. 113).

More than 90% of pregnant women take prescription or over-the-counter (OTC) medications. The findings regarding the teratogenic effects of drugs are mixed, with some studies suggesting potential harm and others suggesting no ill effects of a given drug.

Gary Friedman/Los Angeles Times via Getty Images