Prenatal Evaluations: A Prologue to Postnatal Pathology Interpretations

Animal models are commonly used to investigate the developmental basis of human birth defects. Such models may be used for safety assessment studies designed to reveal xenobiotic-related alterations in juvenile animals, or to investigate gene function or generate models of human disease, as with transgenics. Therefore, the evaluation of rodent embryos and placentas can be used to provide insight into various postnatal abnormalities such as structural or cellular abnormalities and early death. Depending on the defect, pups may be born dead, survive for only a short period of time, survive but with poor growth, or survive and be clinically normal. Mice are generally used to generate genetic alterations that can help in identifying genes involved in embryogenesis. Rats are more commonly used for toxicology studies. This article aims to share information on the importance of, and strategies for, mouse embryo, placenta, and metrial gland evaluations. Information on early postnatal development is also provided as well as select examples of developmental information on organ systems needed for postnatal evaluations. A list of additional studies that can aid in the evaluation of prenatal and postnatal phenotypes is also provided.