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Vol. 12: Fall, 1995
Teratogen Update
From the Editor and Authors:
Birth defects, or congenital anomalies of sufficient magnitude to require medical intervention, are surprisingly common. They occur in 3-5% of newborns. The causes of birth defects remain largely unknown, and currently only about 5% of congenital anomalies are recognized as due to maternal exposures to "environmental" agents, i.e. drugs, viruses, maternal metabolic disorders, or other exposures which may occur during an individual's prenatal development.
Environmental agents which cause birth defects are termed teratogens, and are a cause of great concern to all in our society. This issue of Genetic Drift provides a summary of current scientific knowledge about teratogens, which we hope you will find useful in your practice. It contains a summary of "Etiologies of Malformations," and "Known Human Teratogens."
Teratology information resources are tabulated at the end of our issue and we encourage you to consult them. An additional article in this issue discuss the use of folic acid to prevent neural tube defects.
This issue was spearheaded by Marsha Leen-Mitchell (UT), with contributions from John Carey,MD,(UT), Jean Allen (CO), David Manchester,MD (CO), Dee Quinn (AZ), Gene Hoyme,MD (AZ), and Marcia Feldkamp, MD (UT).
Carol L. Clericuzio, M.D.
Editor
Introduction
In the field of teratology it is vital to critically evaluate the medical and scientific literature. In determining the potential for human teratogenicity of a particular agent many factors must be considered:
- Dosage of Drug or Amount of Exposure
- Timing (Gestational Age at Time of Exposure)
- Route of Administration
- Duration of Exposure
- Species Susceptibility
- Concurrent Exposure to Other Agents
- Maternal Metabolism
- Placental Transport
- Fetal Metabolism
- Clinical Consistency
- No Teratogen Creates Anomalies in All Exposed Fetuses
- Reported Anomalies may have Another Known Cause
These principles were addressed in a previous issue of the Mountain States Regional Genetic Services Network (MSRGSN) Newsletter (1987), available upon request from joyce.hooker@state.co.us.
While very few drugs, chemicals, infections, diseases or other maternal states have been shown to cause congenital abnormalities, there is a public perception (often exacerbated by the media), that most fetal anomalies are related to maternal teratogenic exposures.
In a study conducted by the Pregnancy RiskLine, a telephone teratology information service provided by the University of Utah Division of Clinical Genetics and the Utah Department of Health, ten popular science/health, family, and "women's" magazines, most with circulation of more than one million readers, were found to contain information about pregnancy exposures that was inaccurate, alarming and not supported by the scientific literature. There is, therefore, a tendency for many pregnant women and their families to over-focus on environmental causes of congenital defects.
The Genetic Drift Newsletter is not copyrighted. Readers are free to duplicate all or parts of its contents. The Genetic Drift Newsletter is published semiannually by the Mountain States Genetics Network for associates & those interested in Human Genetics. In accordance with accepted publication standards, we request acknowledgement in print of any article reproduced in another publication. The views expressed in the newsletter do not necessarily reflect local, state, or federal policy. For additional information, contact Carol Clericuzio, M.D., Editor, Department of Pediatrics, The University of New Mexico, Albuquerque, NM, 87131
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