The major objective of our studies in the last decade was a systematic analysis of maternal diseases during pregnancy to reveal their possible adverse effects on birth outcomes. The two most important factors of infant mortality were parti- larly analyzed: structural birth defects, known as congenital abnormalities (CAs) and preterm birth (PB). In general the objectives of scienti c studies might be either to test a new hypothesis or to con rm or confront previously published results. However, less frequently the authors/scientists have personal motivations determined by their professional activities. The authors of this book are practicing physicians and genetic epidemiologist who are mainly interested in the following three practical questions: 1. The possible adverse effects of pharmaceutical products. The possible t- atogenic potential of about 170 drugs has been evaluated very thoroughly using the data set of the Hungarian Case-Control Surveillance of Congenital Abnormalities (HCCSCA) in the last 50 years. These drugs were used to treat maternal diseases and the ndings of our population-based case-control studies will be cited in this book and are shown in the Appendix at the end of the book. However, our long experiences showed two problems in the drug teratology. In general the evaluation of clinical doses of these drugs is a particularly dif- cult challenge due to the modi cation effects of confounders. This problem motivated one of the authors to establish a new model of disaster epidemiology.