Teratology, From the Greek Word

Teratology, from the Greek word "tera" meaning monster, refers to the study of birth defects and their etiology. Statistical analysis of data from teratology studies is complicated by the multiplicity of outcomes that are typically assessed. Indeed, few human teratogens cause a single, uniquely defined defect, but most induce a variety of adverse effects, including major malformations, minor anomalies, and deficiencies in birth weight, length, and head circumference. Sometimes, a particular configuration of effects will be grouped together and identified as a "syndrome." (Legler & Ryan, 1997)

Human teratogens often manifest themselves through a broad spectrum of adverse effects. Although often not serious when considered individually, such outcomes taken together may represent a syndrome that can lead to serious developmental problems. Accordingly, studies that investigate the effect of human teratogens on fetal development typically record the presence or absence of a multitude of abnormalities, resulting in the data of multivariate binary form for each infant. Such studies typically have three objectives: (1) estimate an overall effect of exposure across outcomes, (2) identify subjects having the syndrome, and (3) identify those outcomes that constitute the syndrome so that doctors know what to look for when diagnosing the syndrome in other exposed newborns. This article proposes the use of a logistic regression model with crossed random effect structure to address all three questions simultaneously. (Coull, Hobert, Ryan & Holmes, 2001)

SUMMARY

During the entire life span of each individual, the most dramatic changes take place during the embryonic period. This period is characterized by rapid differentiation. The major parts of all the organ systems of the body are formed during this brief phase, called organogenesis. The speed at which the systems form is astounding. It is even more remarkable that all of them are derived from the same cell formed at fertilization. Since most of the structures in the adult body are established during this brief, seven-week period, it is naturally the most critical time in the entire life span of every individual. Most environmental agents that are harmful to the prenatal human (teratogens such as certain drugs, viruses, and radiation) do their greatest damage during this time. (Bopp, 1985, p. 12) if research in teratology (the study of abnormal development and congenital malformations in embryos and fetuses) establishes links between certain practices or exposures and increased risk of fetal harm, women may be charged with negligence if they bear offspring with defects. (Boling, 1995, p. 11)

Teratogens have been a cause for concern dating back to the early 60's. Among these were thalidomide, rubella ("German" measles), and nicotine (Golden, 1999), retinoids and valproic acid affecting gene/gene, gene/receptor, gene/modifier, and gene/teratogen interactions that lead in neural tube or other structural defects ("Developmental Mechanisms of Human Structural Birth Defects," 2004). Cocaine, which is easily affordable and obtainable in the form of crack, readily crosses the placenta. The incidence of cocaine use by women of childbearing age has been reported to be about 15% and estimates ranged from 10% to 30% of women using during pregnancy in urban centers. Other drugs i.e. alcohol, cigarettes, and marijuana, are frequently used during pregnancy, often in conjunction with cocaine. Ample evidence supports the long-term developmental consequences of these prenatal exposures. Moreover, combinations of these substances may interact in the body to produce more teratogens that are dangerous. (Bendersky, Alessandri, Gilbert & Lewis, 1996)

Many teratogens, however, have much more subtle effects that may not be noticeable at birth. Sometimes months or even years, pass before the damage is recognized. For example, prenatal infection with the parasite Toxoplasma can lead to subtle visual impairment and/or learning disabilities that may not be detected until school age. A pregnant woman may have no noticeable symptoms from toxoplasma infection or just have nonspecific flu-like symptoms. Since the diagnosis of congenital infection with toxoplasmosis can only be confirmed in the newborn period, it is impossible to make a diagnosis in a school-aged child. Therefore, many children who have suffered brain damage from prenatal exposure to damaging agents will remain undiagnosed. (Strom, 1990, p. 71)

Drugs (or teratogens) produce the greatest danger to prenatal development if they are consumed prior to the 45th day after conception, when cell specialization and organ development are accomplished. Drugs that interfere with these processes can have disastrous consequences by altering the normal processes of development and by producing structural defects (congenital malformations) in the child. (Holmes, Reich & Pasternak, 1984, p. 41)