[The month of birth as factor of child survival].

Season of birth may influence considerably children's survival. This study extends the analysis that the authors have already carried out on the Italian regions and Savoy to other countries: Russia, Low Countries, Belgium and Switzerland. The data refer to the second half of the 19th century. It is in Italy that differential mortality according to season of birth is larger (maximum differential in the Venetia region), followed by Russia and Switzerland. Climate's influence (cold in winter and heat in the summer) combine its effects with social customs typical of each country, age and weaning, other customs concerning children's survival. These different combinations determine some unexpected results in the various countries. In the final part of the paper, data derived from family reconstitution of two Tuscan villages (1790-1916) are analysed in order to build a simple model measuring the net impact of climate on mortality during the first two years of life.