Question Answered step-by-step According to chapter 4, many teratogens were described. (1) Provide the definition of what a teratogen is and (2) pick one of the teratogens discussed in the chapter. (3) Describe how it may impact fetal development. (4) Need to go over/ explain the subheadings ( Harmful Substances, Behavioral Teratogens, Risk Analysis,  The Critical Time, Innate Vulnerability, Applying the Research) in the answer. (4) Full explanations and examples are needed. (Include the textbook as a reference) (Chapter 4 information is included) Chapter 4:Harmful Substances A cascade may begin before a woman realizes she is pregnant. Every week, scientists discover another teratogen, which is anything—drugs, viruses, pollutants, malnutrition, stress, and more—that increases the risk of prenatal abnormalities and birth complications.teratogen An agent or condition, including viruses, drugs, and chemicals, that can impair prenatal development and result in birth defects or even death.But do not be alarmed, like one of my students who said that now that she knew all the things that can go wrong, she never wanted to have a baby. As I explained to her, many problems can be avoided, many potential teratogens do no harm, and much damage can be remedied. Thus, prenatal life is not a dangerous period to be feared; it is a natural process to be protected, resulting in a birth that becomes a joyful event.Behavioral Teratogens Some teratogens cause no physical defects but affect the brain, making a child hyperactive, antisocial, or intellectually disabled. These are behavioral teratogens. behavioral teratogens Agents and conditions that can harm the prenatal brain, impairing the future child’s intellectual and emotional functioning.Behavioral teratogens can be subtle, yet their effects last a lifetime. That is one conclusion from longitudinal research on the babies born to women exposed to the influenza pandemic in 1918, which killed more Americans than World War I. By middle age, although some of these babies became wealthy, happy, and brilliant, on average those born in flu-ravaged regions had less education, more unemployment, and lower income than those born a year earlier (Almond, 2006). They died a few years sooner than those born in 1917 or 1919. About 20 percent of all children have difficulties that could be connected to behavioral teratogens, although the link is not straightforward: The cascade is murky.As you remember from Chapter 1, one case proves nothing. J. blames her mother; that may be unfair. Probably several teratogens, genetic risks, inadequate prenatal care, and troubling postnatal experiences are part of her brother’s sorry cascade. It is hard to separate out each risk, but we know that, as much as possible, every risk is to be avoided and every protective factor is to be sought. Part of the problem is that a newborn may appear to have escaped a teratogen (such as alcohol that causes facial deformities or rubella that causes blindness), but the brain is nonetheless damaged. Thousands of babies born each year who appear normal and whose mothers drank alcohol only on weekends are nonetheless affected by fetal alcohol spectrum disorders (Hoyme et al., 2016). The long reach of a seemingly harmless teratogen (in this case, from a mosquito bite) is evident in the Zika virus, which first appeared in 2015 in a few Brazilian newborns with abnormally small brains (microcephaly). Zika is now spreading north, to thousands of babies in many South American nations, in the southeastern United States, and in Puerto Rico. Even those who appear normal are impaired, particularly in their senses and emotions (they are very irritable). Thus, Zika is a behavioral teratogen (Van den Pol, 2017; Rosen, 2016).Risk Analysis Life requires risks: We routinely decide which chances to take and how to minimize harm. To pick an easy example: Crossing the street is risky, yet avoiding street-crossing would harm development. Knowing the danger, we look both ways, and we hold the hands of our young children.Risk analysis is crucial lifelong (Sheeran et al., 2014). You read in Chapter 3 that pregnancy after age 35 increases the chance of many disorders, but it is also true that mature parents are more likely to have happy marriages, intended pregnancies, and a cooperative parental alliance, all of which benefit their children. Pregnancy at any age entails risks and benefits, joys and concerns. Always, risk analysis is needed; many problems can be prevented or overcome.Sixty years ago, risk analysis was not applied to prenatal development. It was assumed that the placenta screened out all harmful substances. If a baby had a birth defect, that was fate—unavoidable. Then two tragic episodes showed otherwise. (1) On an Australian army base, a sudden increase in babies born blind mystified the military doctors. Then they figured it out: The same base experienced a rubella (German measles) epidemic seven months earlier (Gregg, 1941/1991). (2) A tragic rise in British newborns with deformed limbs was traced to maternal use of thalidomide, a new drug for nausea that was widely prescribed in Europe in the late 1950s (Schardein, 1976).Thus began teratology, a science of risk analysis. Although all teratogens increase the risk of harm, none always cause damage; analysis assesses probabilities, not certainties (Aven, 2011). The impact of teratogens depends on the interplay of many factors, both destructive and constructive—an example of the dynamicsystems perspective described in Chapter 1.teratology The scientific study of birth abnormalities, especially on causes of biological disabilities and impairments.For example, twins conceived via in vitro fertilization (IVF) are more likely to be born early and small than are twins conceived naturally, but many factors (where they are born, parents’ SES, and more) increase the odds of healthy newborns (Qin et al., 2017). Thus, parents contemplating IVF need to consider the risks of multiple transfers—but that doesn’t mean no one should ever do it.The Critical Time Timing is crucial. Some teratogens cause damage only during a critical period (see Figure 4.5). [Developmental Link: Critical and sensitive periods are described in Chapter 1.] Consequently, obstetricians recommend that women avoid drugs (including cigarettes and alcohol), supplement a balanced diet with extra folic acid and iron, update their immunizations, and gain or lose weight if needed before pregnancy occurs. Indeed, preconception health is at least as important as postconception health.The first days and weeks after conception (the germinal and embryonic periods) are critical for body formation, but health during the entire fetal period affects the brain. Therefore, behavioral teratogens affect the fetus at any time. Cigarettes, for instance, are harmful whether the mother smokes before or during pregnancy, but quitting by mid-pregnancy protects newborn birthweight (Kvalvik et al., 2017). A longitudinal study of 7-year-olds found that, although alcohol is a teratogen throughout pregnancy, binge drinking is a more potent behavioral teratogen in the second half of pregnancy than in the first (Niclasen et al., 2014). Timing may be important in another way. When pregnancy occurs soon after a previous pregnancy, risk increases. For example, one study found that second-born children are twice as likely to have autism spectrum disorder if they are born within a year of the first-born child (Cheslack-Postava et al., 2011).How Much Is Too Much? A second factor that affects the harm from teratogens is the dose and/or frequency of exposure. Some teratogens have a threshold effect; they are virtually harmless until exposure reaches a certain level, at which point they “cross the threshold” and become damaging. This threshold is not a fixed boundary: Dose, timing, frequency, and other teratogens affect when the threshold is crossed (O’Leary et al., 2010).threshold effect In prenatal development, when a teratogen is relatively harmless in small doses but becomes harmful once exposure reaches a certain level (the threshold).Consequently, experts rarely specify thresholds for any particular drug. For example, alcohol, tobacco, and marijuana are more teratogenic, with a lower threshold for each, when all three are combined. Is there a safe dose for psychoactive drugs? Consider alcohol. During the period of the embryo, a mother’s heavy drinking can cause fetal alcohol syndrome (FAS), which distorts the facial features of a child (especially the eyes, ears, and upper lip). As already mentioned, later in pregnancy, alcohol is a behavioral teratogen, with fetal alcohol ef ects (FAE) possible, not FAS (Hoyme et al., 2016).fetal alcohol syndrome (FAS) A cluster of birth defects, including abnormal facial characteristics, slow physical growth, and reduced intellectual ability, that may occur in the fetus of a woman who drinks alcohol while pregnant.Currently, pregnant women are advised to avoid all alcohol, but many women in France (between 12 and 63 percent, depending on specifics of the research) do not heed that message (Dumas et al., 2014). Most of their babies seem fine. Should all women who might become pregnant refuse a legal substance that most men use routinely? Wise? Probably. Necessary? Maybe not.Innate VulnerabilityGenes are a third factor that influences the effects of teratogens. When a woman carrying dizygotic twins drinks alcohol, for example, the twins’ blood alcohol levels are equal, yet one twin may be more severely affected than the other because of different alleles for the enzyme that metabolizes alcohol. Similar differential susceptibility occurs for many teratogens.The Y chromosome may be critical: Male fetuses are more likely to be spontaneously aborted, stillborn, or harmed by teratogens than are female fetuses. However, the male-female hazard rate differs from one teratogen to another (Lewis & Kestler, 2012). Genes are important not only at conception but also during pregnancy. One maternal allele results in low levels of folic acid in a woman’s bloodstream and hence in the embryo that can produce neural-tube defects— either spina bifida, in which the tail of the spine is not enclosed properly (enclosure normally occurs at about week 7), or anencephaly, when part of the brain is missing. Neural-tube defects are more common in certain ethnic groups (e.g., Irish, English, and Egyptian). In the United States, they are most common in Appalachia.Applying the ResearchRemember that no substance is always teratogenic, and no protective measure always succeeds. This is evident in a study of neural-tube disorder (Smithells et al., 2011). In an application of the research, about half of a group of 550 women who had already given birth to a child with the disorder (and hence were genetically at risk) and who then became pregnant took folic acid supplements. The other half ate normally.The rate of newborns with neural-tube defects was 1 in 250 among the supplemented mothers and 13 in 300 in the nonsupplemented ones, proof that folic acid helps. But note that almost 96 percent of the women who were at genetic risk and did not take supplements had healthy babies. Also note that one supplemented woman gave birth to a second child with a neural-tube disorder. Risk analysis can improve the odds, as it did here, but it does not guarantee.Results of teratogenic exposure cannot be predicted precisely for each individual. Instead, research has discovered many teratogens, as well as what can be done to reduce the risks. One is simply optimal weight gain, which varies depending on preconception weight: Underweight women need to gain more than average and obese women need to gain less.General health during pregnancy is at least half the battle. Women who maintain good nutrition and avoid drugs and teratogenic chemicals (often found in pesticides, cleaning fluids, and cosmetics) usually have healthy babies. Some medications are necessary (e.g., for women with epilepsy, diabetes, and severe depression), but advice regarding specific drugs should occur before conception. Many women assume that herbal medicines or over-the-counter drugs are safe. Not so. As pediatrics professor Allen Mitchell explains, “Many over-the-counter drugs were grandfathered in with no studies of their possible effects during pregnancy” (quoted in Brody, 2013, p. D5). (“Grandfathered” means that if they were legal in days past, they remain legal—no modern testing needed.) Sadly, a cascade of teratogens often begins with women who are already vulnerable and who have no preconception care. For example, smokers are more often drinkers (as was J.’s mother), and migrant workers are more often exposed to chemicals and pesticides, and they rarely have early prenatal care.   Health Science Science Nursing PSY PSY-145 Share QuestionEmailCopy link Comments (0)

Question Answered step-by-step According to chapter 4, many teratogens were described. (1) Provide the definition of what a teratogen is and (2) pick one of the teratogens discussed in the chapter. (3) Describe how it may impact fetal development. (4) Need to go over/ explain the subheadings ( Harmful Substances, Behavioral Teratogens, Risk Analysis,  The Critical Time, Innate Vulnerability, Applying the Research) in the answer. (4) Full explanations and examples are needed. (Include the textbook as a reference) (Chapter 4 information is included) Chapter 4:Harmful Substances A cascade may begin before a woman realizes she is pregnant. Every week, scientists discover another teratogen, which is anything—drugs, viruses, pollutants, malnutrition, stress, and more—that increases the risk of prenatal abnormalities and birth complications.teratogen An agent or condition, including viruses, drugs, and chemicals, that can impair prenatal development and result in birth defects or even death.But do not be alarmed, like one of my students who said that now that she knew all the things that can go wrong, she never wanted to have a baby. As I explained to her, many problems can be avoided, many potential teratogens do no harm, and much damage can be remedied. Thus, prenatal life is not a dangerous period to be feared; it is a natural process to be protected, resulting in a birth that becomes a joyful event.Behavioral Teratogens Some teratogens cause no physical defects but affect the brain, making a child hyperactive, antisocial, or intellectually disabled. These are behavioral teratogens. behavioral teratogens Agents and conditions that can harm the prenatal brain, impairing the future child’s intellectual and emotional functioning.Behavioral teratogens can be subtle, yet their effects last a lifetime. That is one conclusion from longitudinal research on the babies born to women exposed to the influenza pandemic in 1918, which killed more Americans than World War I. By middle age, although some of these babies became wealthy, happy, and brilliant, on average those born in flu-ravaged regions had less education, more unemployment, and lower income than those born a year earlier (Almond, 2006). They died a few years sooner than those born in 1917 or 1919. About 20 percent of all children have difficulties that could be connected to behavioral teratogens, although the link is not straightforward: The cascade is murky.As you remember from Chapter 1, one case proves nothing. J. blames her mother; that may be unfair. Probably several teratogens, genetic risks, inadequate prenatal care, and troubling postnatal experiences are part of her brother’s sorry cascade. It is hard to separate out each risk, but we know that, as much as possible, every risk is to be avoided and every protective factor is to be sought. Part of the problem is that a newborn may appear to have escaped a teratogen (such as alcohol that causes facial deformities or rubella that causes blindness), but the brain is nonetheless damaged. Thousands of babies born each year who appear normal and whose mothers drank alcohol only on weekends are nonetheless affected by fetal alcohol spectrum disorders (Hoyme et al., 2016). The long reach of a seemingly harmless teratogen (in this case, from a mosquito bite) is evident in the Zika virus, which first appeared in 2015 in a few Brazilian newborns with abnormally small brains (microcephaly). Zika is now spreading north, to thousands of babies in many South American nations, in the southeastern United States, and in Puerto Rico. Even those who appear normal are impaired, particularly in their senses and emotions (they are very irritable). Thus, Zika is a behavioral teratogen (Van den Pol, 2017; Rosen, 2016).Risk Analysis Life requires risks: We routinely decide which chances to take and how to minimize harm. To pick an easy example: Crossing the street is risky, yet avoiding street-crossing would harm development. Knowing the danger, we look both ways, and we hold the hands of our young children.Risk analysis is crucial lifelong (Sheeran et al., 2014). You read in Chapter 3 that pregnancy after age 35 increases the chance of many disorders, but it is also true that mature parents are more likely to have happy marriages, intended pregnancies, and a cooperative parental alliance, all of which benefit their children. Pregnancy at any age entails risks and benefits, joys and concerns. Always, risk analysis is needed; many problems can be prevented or overcome.Sixty years ago, risk analysis was not applied to prenatal development. It was assumed that the placenta screened out all harmful substances. If a baby had a birth defect, that was fate—unavoidable. Then two tragic episodes showed otherwise. (1) On an Australian army base, a sudden increase in babies born blind mystified the military doctors. Then they figured it out: The same base experienced a rubella (German measles) epidemic seven months earlier (Gregg, 1941/1991). (2) A tragic rise in British newborns with deformed limbs was traced to maternal use of thalidomide, a new drug for nausea that was widely prescribed in Europe in the late 1950s (Schardein, 1976).Thus began teratology, a science of risk analysis. Although all teratogens increase the risk of harm, none always cause damage; analysis assesses probabilities, not certainties (Aven, 2011). The impact of teratogens depends on the interplay of many factors, both destructive and constructive—an example of the dynamicsystems perspective described in Chapter 1.teratology The scientific study of birth abnormalities, especially on causes of biological disabilities and impairments.For example, twins conceived via in vitro fertilization (IVF) are more likely to be born early and small than are twins conceived naturally, but many factors (where they are born, parents’ SES, and more) increase the odds of healthy newborns (Qin et al., 2017). Thus, parents contemplating IVF need to consider the risks of multiple transfers—but that doesn’t mean no one should ever do it.The Critical Time Timing is crucial. Some teratogens cause damage only during a critical period (see Figure 4.5). [Developmental Link: Critical and sensitive periods are described in Chapter 1.] Consequently, obstetricians recommend that women avoid drugs (including cigarettes and alcohol), supplement a balanced diet with extra folic acid and iron, update their immunizations, and gain or lose weight if needed before pregnancy occurs. Indeed, preconception health is at least as important as postconception health.The first days and weeks after conception (the germinal and embryonic periods) are critical for body formation, but health during the entire fetal period affects the brain. Therefore, behavioral teratogens affect the fetus at any time. Cigarettes, for instance, are harmful whether the mother smokes before or during pregnancy, but quitting by mid-pregnancy protects newborn birthweight (Kvalvik et al., 2017). A longitudinal study of 7-year-olds found that, although alcohol is a teratogen throughout pregnancy, binge drinking is a more potent behavioral teratogen in the second half of pregnancy than in the first (Niclasen et al., 2014). Timing may be important in another way. When pregnancy occurs soon after a previous pregnancy, risk increases. For example, one study found that second-born children are twice as likely to have autism spectrum disorder if they are born within a year of the first-born child (Cheslack-Postava et al., 2011).How Much Is Too Much? A second factor that affects the harm from teratogens is the dose and/or frequency of exposure. Some teratogens have a threshold effect; they are virtually harmless until exposure reaches a certain level, at which point they “cross the threshold” and become damaging. This threshold is not a fixed boundary: Dose, timing, frequency, and other teratogens affect when the threshold is crossed (O’Leary et al., 2010).threshold effect In prenatal development, when a teratogen is relatively harmless in small doses but becomes harmful once exposure reaches a certain level (the threshold).Consequently, experts rarely specify thresholds for any particular drug. For example, alcohol, tobacco, and marijuana are more teratogenic, with a lower threshold for each, when all three are combined. Is there a safe dose for psychoactive drugs? Consider alcohol. During the period of the embryo, a mother’s heavy drinking can cause fetal alcohol syndrome (FAS), which distorts the facial features of a child (especially the eyes, ears, and upper lip). As already mentioned, later in pregnancy, alcohol is a behavioral teratogen, with fetal alcohol ef ects (FAE) possible, not FAS (Hoyme et al., 2016).fetal alcohol syndrome (FAS) A cluster of birth defects, including abnormal facial characteristics, slow physical growth, and reduced intellectual ability, that may occur in the fetus of a woman who drinks alcohol while pregnant.Currently, pregnant women are advised to avoid all alcohol, but many women in France (between 12 and 63 percent, depending on specifics of the research) do not heed that message (Dumas et al., 2014). Most of their babies seem fine. Should all women who might become pregnant refuse a legal substance that most men use routinely? Wise? Probably. Necessary? Maybe not.Innate VulnerabilityGenes are a third factor that influences the effects of teratogens. When a woman carrying dizygotic twins drinks alcohol, for example, the twins’ blood alcohol levels are equal, yet one twin may be more severely affected than the other because of different alleles for the enzyme that metabolizes alcohol. Similar differential susceptibility occurs for many teratogens.The Y chromosome may be critical: Male fetuses are more likely to be spontaneously aborted, stillborn, or harmed by teratogens than are female fetuses. However, the male-female hazard rate differs from one teratogen to another (Lewis & Kestler, 2012). Genes are important not only at conception but also during pregnancy. One maternal allele results in low levels of folic acid in a woman’s bloodstream and hence in the embryo that can produce neural-tube defects— either spina bifida, in which the tail of the spine is not enclosed properly (enclosure normally occurs at about week 7), or anencephaly, when part of the brain is missing. Neural-tube defects are more common in certain ethnic groups (e.g., Irish, English, and Egyptian). In the United States, they are most common in Appalachia.Applying the ResearchRemember that no substance is always teratogenic, and no protective measure always succeeds. This is evident in a study of neural-tube disorder (Smithells et al., 2011). In an application of the research, about half of a group of 550 women who had already given birth to a child with the disorder (and hence were genetically at risk) and who then became pregnant took folic acid supplements. The other half ate normally.The rate of newborns with neural-tube defects was 1 in 250 among the supplemented mothers and 13 in 300 in the nonsupplemented ones, proof that folic acid helps. But note that almost 96 percent of the women who were at genetic risk and did not take supplements had healthy babies. Also note that one supplemented woman gave birth to a second child with a neural-tube disorder. Risk analysis can improve the odds, as it did here, but it does not guarantee.Results of teratogenic exposure cannot be predicted precisely for each individual. Instead, research has discovered many teratogens, as well as what can be done to reduce the risks. One is simply optimal weight gain, which varies depending on preconception weight: Underweight women need to gain more than average and obese women need to gain less.General health during pregnancy is at least half the battle. Women who maintain good nutrition and avoid drugs and teratogenic chemicals (often found in pesticides, cleaning fluids, and cosmetics) usually have healthy babies. Some medications are necessary (e.g., for women with epilepsy, diabetes, and severe depression), but advice regarding specific drugs should occur before conception. Many women assume that herbal medicines or over-the-counter drugs are safe. Not so. As pediatrics professor Allen Mitchell explains, “Many over-the-counter drugs were grandfathered in with no studies of their possible effects during pregnancy” (quoted in Brody, 2013, p. D5). (“Grandfathered” means that if they were legal in days past, they remain legal—no modern testing needed.) Sadly, a cascade of teratogens often begins with women who are already vulnerable and who have no preconception care. For example, smokers are more often drinkers (as was J.’s mother), and migrant workers are more often exposed to chemicals and pesticides, and they rarely have early prenatal care.   Health Science Science Nursing PSY PSY-145 Share QuestionEmailCopy link Comments (0)