ABSTRACT
One of the major concerns of regulatory agencies such as the FDA and EPA, is the evaluation or assessment of risk to unborn fetuses as a result of maternal exposure to hazardous compounds. Since the evaluation of such risks in humans by clinical trials is unethical, preclinical teratology experiments, usually with rodents, are often performed. In such studies, pregnant mice are treated with the compound under investigation, and several measurements are recorded on the fetuses or pups in each litter. The endpoints recorded usually include binary indicators of fetal death or malformation, and continuous measurements, such as fetal weight or length. The common feature in such studies is that measurements and responses within each cluster (i.e., litter) are dependent.
