The term teratogen (Greek word ‘teras’ =“malformation” ) refers to any environmental agent that causes damage during the prenatal period. The teratogens in prenatal development can be a drug, chemical, virus, or other factor that produces a birth defect.
Although it is the job of the placenta to keep teratogens from reaching the fetus, the placenta is not entirely successful at this, and probably every fetus is exposed to some teratogen in prenatal development. The timing and quantity of exposure to a teratogen are crucial. At some phases of prenatal development, a certain teratogen may have only a minimal impact. At other periods of prenatal development, the same teratogen may have profound consequences. Generally, teratogens have their largest effects during periods of especially rapid prenatal development. For example, living in poverty increases the chances of exposure to teratogens in prenatal development.
Mothers who are poor may not be able to afford adequate diets, and they may not be able to afford adequate medical care, making them more susceptible to illnesses that can damage a developing fetus. They are also more likely to expose to pollution. So, it is important to consider the social factors that permit exposure to teratogens.
Contents
Effect of Teratogen in Prenatal Development depends on the following factors:
1. Dose- Larger doses over longer time periods usually have more negative effects.
2. Heredity. – The genetic makeup of the mother and the developing organism plays an important role some are better able than others to withstand harmful environments.
3. Other negative influences.- poor nutrition, and lack of medical care, can worsen the impact of a harmful agent.
4. Age.- The effects of teratogens vary with the age of the organism at time of exposure. for example Sensitive period – If the environment is harmful, then damage occurs, and recovery is difficult and sometimes impossible.
1) Infertility: –
Some 15 percent of couples suffer from infertility, the inability to conceive after 12 to 18 months of trying to become pregnant. Infertility is negatively correlated with age. The older the parents, the more likely infertility will occur. Countries like India with high fertility rates are paradoxically showing increasing incidence of infertility. This is termed as “barrenness amid plenty.” If “age but no birth” definition is used, the percentage of primary infertility in India is 3.9 percent (age standardized to 25-49 years) and 16.8 percent (age standardized to 15 49 years) (Hajela et al., 2016).
2) Miscarriage And Abortion: –
A miscarriage-known as a spontaneous abortion occurs when pregnancy ends before the developing child is able to survive outside the mother’s womb. The embryo detaches from the wall of the uterus and is expelled. Some 15 percent to 20 percent of all pregnancies end in miscarriage, usually in the first several months of pregnancy. Many miscarriages occur so early that the mother is not even aware she was pregnant and may not even know she has suffered a miscarriage (Mismiscarriage).
3) Mother’s Diet: –
Most of our knowledge of the environmental factors that affect the developing fetus comes from study of the mother. So, a mother’s diet plays an important role in bolstering the development of the fetus. A mother who eats a varied diet high in nutrients is apt to have fewer complications during pregnancy, an easier labor, and a generally healthier baby than a mother who diet is restricted in nutrients (Guerrini. Thomson, & Gurling, 2007, Marques 2014).
4) Mother’s Age: –
More women are giving birth later in life than was true two or three decades ago. The cause for this change is largely due to transformations in society, as more women choose to continue their education with advanced degrees and to start careers prior to giving birth to their first child (Gibbs, 2 Wildberger, 2003, Bornstein et al., 2006). Consequently, the number of women who give birth in their 30s and 40 grown considerably since the 1970s.
However, this delay in childbirth has potential consequences for both mothers and children’s health. Women over 30years are at greater risk for a variety of pregnancy and birth completions than younger ones. They are more apt to give birth prematurely and their children are more likely to have low birthweights. This occurs in part cause of a decline in the condition of a woman’s eggs; by the time he is 42 years old, 90 percent of a woman’s eggs are no longer normal (Chatting Berendes, & Forman, 1993, Gibbs, 2002).
Older mothers are also considerably more likely to give birth to children with Down syndrome, some research shows that older mothers are not automatically at risk for more pregnancy problems. Women in their 40s more likely to have prenatal problems than those in their 20s (Ales, Druzin, & Santini, 1990, Dildy e al., 1996).
5) Mother’s Health: –
Mothers who eat the right foods, maintain an appropriate weight, and exercise appropriately maximize the chances of having a healthy baby. Furthermore, they can reduce the lifetime risk of obesity, high blood pressure, and heart disease in their children by maintaining a healthy lifestyle (Walker & Humphries, 2005, 2007).
In contrast, illness in a pregnant woman can have devastating consequences. For instance, the onset of rubella (German measles) in the mother prior to the eleventh week of pregnancy is likely to cause serious consequences in the baby, including blindness, deafness, heart defects, or brain damage. Chicken pox may produce birth defects. Mumps may increase the risk of miscarriage.
Some sexually transmitted diseases, such as syphilis, Gonorrhea, AIDS etc can be transmitted directly to the fetus, who will be born suffering from the disease through the birth canal to be born.
6) Mother’s Drug Use: –
A mother’s use of many kinds of drugs-both legal and illegal-poses serious risks to the unborn child Even over-the-counter remedies for common ailments can have surprisingly injurious consequences. For instance, aspirin taken for a headache can lead to fetal bleeding and growth impairments (Tsan-tefski, Humphreys, & Jackson 2014)
Thalidomide (1950s) for morning sickness during their pregnancies inhibited the growth of arms and legs. In 1970s, the artificial hormone DES (diethylstilbestrol) was frequently prescribed to prevent miscarriage Only later was it found that the daughters of mothers who took DES stood a much higher-than normal chance of developing a rare form of vaginal or cervical cancer and had more difficulties during their pregnancies. Sons of the mothers who had taken DES had their own problems, including a higher-than-average rate of reproductive difficulties (Schecter Finkelstein, & Koren, 2005).
Birth control or fertility pills can also cause fetal damage Such medicines contain sex hormones that affect developing brain structures in the fetus and can cause significant damage (Miller, 1998. Brown, Hines, & Fane, 2002).
Illicit drugs may greater risks for environments of prenatal children. The purity of drug purchased illegally varies significantly, so drug users can never be quite sure what specifically they are ingesting. Furthermore, the effects of some commonly used illicit drug can be particularly devastating (Jones, 2006; Mayes et al., 2007)
Marijuana used during pregnancy can restrict the oxygen that reaches the fetus Its use can lead to infants who are irritable, nervous, and easily disturbed. Children exposed to marijuana prenatally show learning and memory deficits at the age of 10 (Williams & Ross, 2007; Goldschmidt et al., 2008. Willfor Richardson, & Day, 2012).
Cocaine (1990s) use by pregnant women led to an epidemic of thousands of so-called crack babies. Cocaine produces an intense restriction of the arteries leading to the fetus, causing a significant reduction in the flow of blood and oxygen, increasing the risks of fetal death and a number of birth defects and disabilities (Schuetze, Eiden, & Coles, 2007)., shorter and weigh less than average, may have serious respiratory problems. visible birth defects, or seizures ; once they start to cry, it may be hard to soothe them (Singer et al., 2000, Eiden, Foote, & Schuetze, 2007 Richardson, Goldschmidt, & Willford, 2009).
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Reference.
- Robert. S. Feldman. (2017). Development Across the Lifespan. (8th ed.). Pearson Education.
- Laura. E. Berk. (2018). Development Through the Lifespan (7th ed.). Pearson Education.