Frequent deaths of children deeply influenced the general death rate in the past. The curve of natimortality nearly created the curve of general mortality, because very many new-boms died during the first year of life. This was affected by the standard of breastfeeding in a given society, so the rate of natimortality, as well as the general infant mortality was markedly different locally. The infant mortality in two adjoining towns of Frýdek and Místek kept above 500%o until the mid-19th century and it droped below this limit as late as the second half of the 19th century, though slightly (439%o in Frýdek, 457%o in Mistek). The difference between the situation in both towns manifested itself in the categories of foetal mortality and perinatal mortality. In Frýdek, the perinatal mortality was lower, but the foetal mortality was higher than in Mistek. That is why these categories were examined in this article in greater detail with regard to the complicated classification of the „time of death“ of newly-born children, as well as the leakage of foetal mortality data, and with regard to the problems of spontaneous abortions or infanticide. Causes of deaths were taken into account too, nevertheless only within the classification of diseases used at that time, it means especially the rate of various accidents, incl. abortions, the extent of influence that infectious diseases and avitaminosis exerted on the death rate.