toxicant should be brought forward for further investigation, such as more rigorous epidemiological characterization of the correlation of exposure and birth defect and more incisive animal testing to ascertain dose-response relationships.
In addition to case reports, there are both active and passive birth defects surveillance systems in place, both nationally and internationally (NBDPN 2000). They vary in quality and completeness. A number of established non-governmental databases are used to monitor drug exposures and developmental defects, and these are frequently used in pharmacoepidemiology studies (Strom 1994).
A recent study entitled “Healthy from the Start: Why America Needs a Better System to Track and Understand Birth Defects and the Environment” and conducted by the Environmental Health Commission (Goldman et al. 1999) evaluated the quality of state tracking systems for birth defects. The study analyzed existing data from those systems and looked at the connection between environmental agents and birth defects. The authors concluded that the majority of states either do not have a tracking system or have one that is inadequate. They concluded that the data are inadequate to draw conclusions about the role of environmental exposures in causing birth defects and recommended that a national effort for tracking birth defects and a national approach for monitoring environmental exposures be established.
Those state tracking systems currently in place are usually either active or passive systems. In an active surveillance system, such as that administered by the Centers for Disease Control and Prevention, trained personnel actively seek data from sources such as vital records and hospital reports. Passive case identification involves relying on patients and health care providers to voluntarily report exposures (usually drug exposures) and outcomes (Strom 1994); follow-up is minimal or nonexistent. Passive, voluntary reporting of systems have several limitations, including under-reporting of adverse events, incomplete information on cases, and the retrospective nature of most adverse event reports (i.e., the reports are made after an adverse pregnancy outcome has occurred), and the true denominator for exposed pregnancies is not known.
There are a number of pregnancy registries currently being conducted (Weiss et al. 1999). For example, the North American Registry for Epilepsy and Pregnancy is a surveillance program to monitor pregnancy outcomes in women taking antiepileptic drugs (NAREP 1998). Some prospective post-surveillance follow-up studies have been directed by pharmaceutical companies evaluating post-marketing impacts of drugs. The committee suggests that the data from pharmaceutical company studies be made available and that the existing efforts to track human developmental outcomes be better characterized and recognized. Improvements could include making various information from epidemiology databases accessible via the Internet.
There are databases for which known genetically based malformations are linked with databases for specific clinically described syndromes. One example of such a database is the On Line Mendelian Inheritance in Man (OMIM) data-