Teratogens

The World Health Organization estimates that 15% of all clinically recognizable pregnancies end in abortion. Of these, 50-60% are due to chromosomal abnormalities. In addition, 3-6% of all offspring are malformed. The causes of these malformations can be divided into three categories: unknown, genetic, and environmental. Environmental causes only account for 10% of all congenital malformations and can be further divided into maternal conditions, infectious agents, mechanical problems (deformations), and chemicals (including prescription drugs and high-dose ionizing radiation). Chemical environmental causes include consumption during pregnancy of the teratogenic agents discussed later. These account for less than 1% of all congenital malformations but are important in that the exposures to these chemicals may be preventable.

Several anticancer drugs cause problems for fetal development. Aminopterin can induce abortion within its therapeutic range, and it causes microcephaly, hydrocephaly, cleft palate, meningomyelo-cele, intrauterine growth retardation, abnormal cranial ossification, and mental retardation. Cyclo-phosphamide interacts with DNA and can result in cell death. Its use during pregnancy can result in growth retardation, ectrodactyly, syndactyly, and cardiovascular anomalies.

Some antibiotics cause abnormal fetal development if taken by the pregnant woman. Streptomycin can cause hearing problems, although the risk of this is quite low. Tetracycline may produce staining of the teeth and bones if taken late in the first trimester or during the last two trimesters.

Anticonvulsants can also cause adverse pregnancy outcomes. Carbamazepine produces minor craniofa-cial defects, fingernail hypoplasia, and developmental delays. Trimethadione causes 'fetal trimethadione syndrome,' characterized by V-shaped eyebrows, low-set ears, a high-arched palate, irregular teeth, central nervous system anomalies, and severe developmental delays. Valproic acid causes spina bifida and facial dysmorphology in the fetus of 1% of pregnant users.

Other potentially teratogenic drugs include andro-gens, which result in masculinization of the embryo and stimulate growth and differentiation of sex steroid receptor-containing tissues. Angiotensin-converting enzyme inhibitors are antihypertensive agents that have detrimental effects during the second and third trimesters, including fetal death, oligohydramnios, pulmonary hypoplasia, neonatal anuria, intrauterine growth retardation, and skull hypoplasia. The pregnant woman who uses cocaine risks preterm delivery, fetal loss, intrauterine growth retardation, microcephaly, neurobehavioral abnormalities, vascular disruptive phenomena, cerebral infarctions, and certain types of visceral and urinary tract malformations. Coumadin, a vitamin K analog, is an anticoagulant and in the first trimester can produce malformations, including nasal hypoplasia, stippling of secondary epiphysis, intrauterine growth retardation, and anomalies of the eyes, hands, neck, and central nervous system. Lithium carbonate, an antidepressant, has teratogenic effects in animals but these have not been confirmed in humans.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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