Teratogens are the agents that can cause abnormities during a prenatal development. The effects of Teratogen depend on the stage of the prenatal development and amount of exposure. Everyone is exposed to environmental hazards but expectant women face a higher risk environmental Teratogens because it is very difficult detect to establish their presence. On the other hand, in order to reduce the effects of Teratogens, it is important that an expectant woman should exposure even to other teratogenic agents like alcohol and nicotine especially during a prenatal period. The effects can be seen in the later stages of childhood life as well.
The prenatal period from conception and extends up to child delivery. The first period of the prenatal development lasts two weeks. During a germinal stage, the zygote repeatedly divides but does not gain in mass. It begins when an ovum is fertilized by the sperm in the oviducts. It ends when the fertilized one has implanted itself in the walls of the uterus (Kail & Cavanaugh, 2012). Once implanted in the uterine wall, it obtains nourishment from the mother. Then, it takes a form of a blast cyst. By the end of this period, the outer part of the blast cyst differentiates into membranes that will protect and nourish the embryo.
The second period starts two weeks after the conception and eight weeks after. It is commonly referred to as a fetal period. Rapid growths in which major parts of the body are created occur in this period (Kail & Cavanaugh, 2012). The heart begins to function during the fourth week. By five to six weeks, the embryo has undifferentiated sex organs that resemble female structures. Testes produce male sex hormones that spur the development of male genital organs and a male duct system. The third period of the prenatal development begins at 9 weeks and lasts until delivery. There are remarkable changes in the size of the fetus. By the end of seven months, most of body systems are functioning well. There is an increase in the functions of the heart and lungs that can sustain life.
Teratogens are the agents that can cause potential hazardous effects and abnormities during the prenatal development. These include agents such as prescription drugs, chemicals related to environmental exposure, maternal medical conditions, alcohol, and nicotine. Environmental Teratogens are particularly dangerous because a pregnant woman may not be aware that these substances are present. They are not readily available (The effects of Teratogen depend on the stage of the prenatal development and amount of exposure. For instance, everyone is exposed to some radiation like sun rays. It causes no harm. However, large doses of radiations can cause serious fetal defects that can lead to death. In some cases, the effects are not evident until later stages of life. In addition, the timing of the teratogenic insult makes a significant impact on the damage done to the fetus (Kail & Cavanaugh, 2012). If it is introduced before implantation, the zygote is destroyed. Otherwise, it appears unaffected, if it occurs during the formation of main systems of the body (in the second to eight weeks of pregnancy); the fetus is very vulnerable to any injury.
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In the third trimester, the potential for harm decreases because most of organs of the fetus are formed and merely maturing. A teratogen may cause its effects by a number of different pathophysiological mechanisms including the cell death, alterations of cell division, and the tissue growth. They interfere with cellular differentiation. Its effects also differ depending on the genetic susceptibility of the embryo or fetus and how it reaches the prenatal environment (Kail & Cavanaugh, 2012). It is after a teratogen gains an access to the fetus that can cause harmful effects. There are some teratogenic agents that are not capable of causing harm because of their size and binding properties restrict them from crossing the placenta. These effects are non-genetic. Thus, they are not inherited by the subsequent generations (Kail & Cavanaugh, 2012). A teratogen may damage the embryo directly or by disrupting a normal functioning of the placenta by which the fetus receives nutrients, thereby creating an abnormal uterine environment. In relation, the greater the exposure is the greater the risk to the fetus is. However, different individuals show different levels of the susceptibility to the teratogenic effect.
Ingested Teratogens- most substances consumed by a pregnant woman pass to the fetus from a maternal blood stream through the placenta and then get into the fetal circulation. Commonly, these include the prescription of medications, illicit drugs, and alcohol (Klossner & Hatfield, 2006). Some drugs may be therapeutic for the mother but also have the teratogenic effects to the fetus; for example, phenytoin is used in a therapy for preventing seizures. However, it is also known to cause abnormalities such as cleft palate. However, not all medications are harmful. Some drugs such as heparin are not able to cross a placental barrier; and, thus, it is safe to use during pregnancy. Additionally, one of the fetus’ main body systems affected throughout the embryonic and fetal period is a brain and a central nervous system (Klossner & Hatfield, 2006). On the other hand, infectious Teratogens occur when a woman develops some infection during her pregnancy. In this case, the infection can pass to the fetus and affect its development. Some common infections include the varicella, rubella, and cytomegalovirus. Further, an expectant woman may be exposed to the environmental hazard such as ionizing X-rays and radioactive substances that can cause birth defects (Klossner & Hatfield, 2006). It is important to use a Lead shield for unavoidable rays and wearing gloves when handling chemicals in order to protect the developing fetus.
The harmful impact of prenatal exposure to drugs is catalyzed by their timing, amount of dosage and the degree to exposure. For instance, throughout the prenatal period and post natal exposure, Amphetamine can result o low birth weights, decreased arousal and deficits in intellectual development. Second, Valproate is a commonly prescribed drug as an anti-convulsant and ant mania therapeutic. Clinical data demonstrate that it is associated with increased teratogenic effects of defects in the neural tube and cranial face dysmorphia. Terbutaline and other similar drugs are commonly administered to reduce premature uterine contractions in the late- term pregnancies. However, its exposure results in neuron inflammation and cellular defects. Furthermore, children who are exposed to Terbutaline during the third trimester have decreased learning abilities and neuro-psychiatric disorders.
Many different drugs are able to cross a placental barrier and cause a teratogenic effect. Thalidomide as a prescribed drug for relieving nausea and as a sedative in pregnant women causes defects to the limbs. Affected infants typically have incomplete developed arms or legs. One dose of thalidomide is sufficient to induce such deformities (Thompson & Stanwood, 2009). Antibiotics like Tetracycline and Sulfonamides cause tooth enamel deficiencies and possibly long-bone deformities. Anticonvulsants such as Dilantin and Valproic acid can lead to some anomalies of a fetal hydration syndrome and neural tube defects. Epileptics who take anticonvulsants during pregnancy may give birth to babies with distinctive facial features and heart defects caused by the drug. Further, Ant diabetic agents used to lower blood glucose causes neonatal hypoglycemia while anticoagulants lead to fetal bleeding. Women who are using these agents should avoid conceiving by using family planning methods.
Chemicals Related to Environmental Exposure
Environmental agents mostly causes effects at very early stage of development .However, the teratogenic effects of hazardous environmental agents can be detected in future lives for instance during the time of sexual maturation (Mattison et al, 2003). Some events in the external environment can affect it indirectly through the mother. Prenatal exposure to heavy metals threatens the cognitive development; for instance, mercury is connected with the neurological damage. Exposure to PCBs is closely associated with underweight babies, less responsiveness, and the higher likelihood of developing cognitive defects. Excessive fetal exposure to radiation may cause neural and skeletal problems. In addition, maternal stress is linked to the secretion of hormones such as adrenaline which passes through the placenta. It is closely tied it complications in pregnancy such as difficult labor, preterm birth and irritable babies with low birth weights (Mattison et al, 2003). In relation, pregnant women should reduce their exposure to radiographic agents. All females should have abdominal shielding for X-ray procedures.
Maternal drinking during pregnancy, may affect the neurodevelopment. The prenatal exposure to alcohol represents an important risk factor to disability which could be potentially preventable (Gray, 2009).Alcoholic effects can occur at any time during pregnancy, but they are particularly sensitive between eight and twelve weeks. The connection between alcohol and prenatal development is clear. Fetal alcohol syndrome represents the most severe manifestation of heavy intakes. The syndrome has features such as growth deficiency and facial anomalies. It should be avoided by both an expectant mother and those that are planning to carry pregnancy because there is no recommended limit of alcohol consumption during this period. It is associated with fetal alcohol syndrome, miscarriages and low birth weight.
Exposure to cigarette smoking is a major cause of mortality for both an expectant women and her fetus. Damage from maternal smoking has direct adverse effects on placental development. These effects decrease the transfer of nutrients and oxygen to the fetus therefore leading to premature birth and fetal growth restriction (Blood-Siegfried & Rende, 2010). Exposure to nicotine results to other problems that can last even into adulthood. Smoking during pregnancy accounts for as 161,000 prenatal and 4800 infant deaths in the United States annually. More than half of these cases are classified as sudden infant death syndrome. Although paternal smoking and exposure to other forms of tobacco smoke increases the risk, it is highest when smoked by an expectant mother. Other tobacco related effects include increased risk of childhood asthma and respiratory infections. It increases the risk of cognitive deficits that are apparent at later childhood.
Maternal Medical Conditions Such as Diabetes and epilepsy
Babies born to epileptic mothers are at a significant developmental risk during pregnancy especially due to maternal seizures and teratogenic effects of antiepileptic drugs. The social family conditions associated with looking after a chronically sick mother can also have harmful effects on the baby (Titze et al, 2008). When follow up is conducted on children born to mothers with epilepsy and the non-affected ones. The findings show that children who were exposed to antiepileptic drugs achieved lower IQs. Generalized seizures during pregnancy observed half the mothers, did not exuberate this effect. In addition to the medical conditions of the expectant mother, the quality of the family support can have various o n intellectual development of her baby (Titze et al, 2008).
Babies with exposure to prenatal risk appeared to be more vulnerable to environmental disadvantage. The effects are prominent when combine to other factors such as depression and anxiety. The status of epileptics is highly linked to still births, miscarriage and even death as a result of apnea (Titze et al, 2008). Diabetes mellitus may be associated with abnormal embryogenesis particularly if the diabetic condition of a pregnant woman is poorly controlled in the first trimester. For instance, cardiac malformation occurs three times more often in babies born by diabetic mothers than healthy one. Similarly, a caudal regression syndrome with fusion of legs is a rare disorder but is being common in the babies of diabetic mothers.
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The prenatal period starts from conception and extends up to child delivery. In other words, it begins when an ovum is fertilized by the sperm in the oviducts and ends when the fertilized one has implanted itself in the walls of the uterus Teratogens cause some effects on the prenatal development. Therefore, pregnant women should avoid exposure especially to environmental hazards, alcohol, and nicotine. A mother with medical conditions such as diabetes should seek for the medical advice regarding the medications in order to establish whether the fetus is at a potential risk of teratogenic effects of the prescribed drugs or not. These effects range from deficiencies in growth, poor intellectual cognitive abilities, low birth weights and even death. Teratogenic effects can be prominent even in later stages of childhood life.