Chemically Induced Birth Defects

Abstract

Seeing a new edition of this classic and informative text is like visiting an old college classmate after an absence of many years — the contours of shared experience form the basis for renewal through updating the path of life's course in the intervening period. Schardein has retained the basic structure of his compendious reference work while incorporating new information and revising sections where studies from animal models, toxicology, and developmental and reproductive epidemiology have provided new insights. The purpose of the text, in the author's words, is ''to catalog the available data on drugs and chemicals with respect to their potential teratogenicity in animals and humans'' (p. vi). This is accomplished through a series of chapters, divided into two parts, one focused on drugs, and the other on chemicals, which follow an introduction to the principles of teratogenesis relevant to drug and chemical exposures. Most of the substantive chapters are organized in a familiar manner, beginning with a general introduction, then taking each class of potential exposures in turn, first reviewing the literature on animal studies and then considering the research in humans. The chapters end with a concluding section and a lengthy set of references. Approximately three-fourths of the text is devoted to drugs and their effects on the developing fetus. This section includes 23 separate chapters, covering medications used to treat specific diseases and organisms as well as drugs used for body system-specific ailments. There are also chapters on food additives and dietary issues, and on ''personal and social drugs.'' The chapters vary in comprehensiveness and balance between animal model and human studies. The text is not current in some areas. For example, birth defects surveillance in the United States has progressed rapidly in the 1990s beyond the point discussed on p. 80, and the reference to the number of pregnancies affected by anticonvulsant therapy each year dates to 1984 (p. 179). On the other hand, the chapter on thalidomide reflects recent developments in its use and national postmarketing surveillance activities. The section on chemical exposures includes nine chapters focusing on metals, industrial solvents, diagnostic agents, plastics, toxins, and pollutants as well as miscellaneous chemicals. The section begins with a general chapter on the nature of chemical exposures in pregnancy. This chapter, although excellent in content, appears to have been last revised in 1996 and does not include new references in this rapidly evolving field of clinical and epidemiologic research. One might legitimately question the need for a text of this nature in the future. A CD-ROM or interactive web-based application might make the essential information easier to access. As an experiment, this reviewer attempted to quickly locate information concerning the teratogenicity of human exposure to acetaminophen, PCBs, and anticonvulsant medications. For acetaminophen, the table of contents identified a chapter on ''Agents Used for Pain.'' The outline for this chapter has a section on ''Analgesics, Anti-inflammatory and Antipyretic Agents.'' Turning to this section, there is a single paragraph on animal research with a summary table indicating no association in the rat and mouse models. Following this table, there is a section on human experience, in which a paragraph reviews the research on acetaminophen exposure in women. The index faithfully identifies these pages in the text. For PCBs, the table of contents did not give a clear indication of which chapter to examine first. Turning to the index, the entry under PCBs refers the reader to 10 page references, together with two subheadings with similar page references. For anticonvulsant medications, there is a clearly identified chapter in the table of contents and a detailed listing in the index as well. While the references do not always point to the latest research, they are comprehensive in detailing the history of research concerning each drug or chemical. There will always be a need for comprehensive texts like Schardein's, but the author should give some thought to methods for integrating its content with relational database or Internet-based methodologies of information delivery. It is unlikely that anyone will sit down and read this book cover to cover. However, it is comforting to know that it can be found on the clinician or perinatal researcher's reference shelf when it is needed. Each chapter stands on its own merits as a comprehensive review of its subject, and this reviewer expresses the hope that a reader who can find the resources listed in each chapter will also be able to utilize Medline or PubMed to find the current literature as well. Active perinatal practices and training programs should have access to the latest edition of this text, and hospital libraries supporting specialists in perinatology and neonatology should include it in their reference collections.