Birth defects and disturbances in growth and development need an increasing attention in perinatal medicine. It is remarkable that so little attention has been paid to the pathogenesis of malformations in the literature in an approach to find aspects of prevention. Primary prevention of birth defects is an important public health issue as malformations have important consequences both for society and the individuals concerned. Prepregnancy care as a logical precursor to antenatal care, offers risk-assessment, advice and occasionally treatment before pregnancy, in order to avoid congenital malformations. It is therefore that we started a research program with emphasis on primary prevention of congenital malformations. In this respect medication, maternal nutritional status, diabetes mellitus and neural tube defects are discussed.