In the last century, biomedical science and clinical practice have dramatically altered the biological characteristics of women of reproductive age. Medical personnel have become increasingly familiar with both “saving” and preserving conception, and in adequately treating placentas and “threatened” fetuses, from the moment of fertilization to implantation, up to the end of pregnancy. Assisted reproduction has introduced postmenopausal pregnancies and increased the incidence of multiple gestations, which contributed to transforming the epidemiology of maternal and perinatal morbidity and mortality. Several non-lethal, acquired, and hereditary conditions have become part of the science of reproduction. The study concerning the natural history of pregnancy that coexists or imposes itself on disease and medical treatment, today, represents a young clinical science, with much more to learn, including the argued need to sometimes have to discourage a possible pregnancy. On the one hand, the decline in the number of deaths from bleeding and obstructed labor is gratifying. On the other hand, the increase due to the progression of the so-called “other causes” constitutes a serious concern and pushes clinical and basic research to focus more on periconceptional medicine and screening.