The normal development of the fetus depends upon a complicated interaction of both genetic and nongenetic factors.
Many chemicals may pass the placental barriers to induce a A teratogenic effect on the fetus.
Many of drugs , nutrients or environmental factors may cross the placenta including;
1-Alcohol— It induces the Fetal alcohol syndrome (FAS) (a defect that is becoming more widely known} The symptoms of FAS are small head and body, a flattened face, distinctive eyes, retarded physical growth, mental retardation, shorter and lighter in weight than normal, heart defects, and poor coordination.
2- Tobacco—Smoking after the fourth month of pregnancy is a major cause of prematurity and the birth of underweight babies. Smoking can also increase the chances of bleeding during pregnancy, miscarriage, premature rupture of the membranes, hemorrhage before or early in labor, hemorrhage after delivery, congenital abnormality, stillbirth, and death of the baby in the week following delivery.
3- Caffeine—Tests done with animals have indicated that caffeine can cause deformities in skeletal and bone development.
4-Aspirin—is a potent drug since it is so widely used and easy to obtain. Studies with animals show aspirin may interfere with blood clotting in the fetus with potential for brain damage.
5-Barbiturates and Amphetamines—The baby may be addicted and have to go through withdrawal. With barbiturates, the baby may have tremors, restlessness, and irritability and amphetamines may cause birth defects.
6-Antibiotics—Tetracycline should not be used during pregnancy. It has been found it can effect the growth of the baby’s bones during the time when it is taken. Also it may cause yellow mottling and staining of the baby’s first teeth. Streptomycin should not be taken since it can cause deafness in the baby.
7- Many other chemicals that are categorized as environmental hormones such as DDT that is widely used as insecticidals and also DPT that is used in many of the domestic food preservation...etc.
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