Among the 85,976 children born at the «Istituto Ospitaliero Provinciale per la Maternità di Milano» from January 1st 1942 through December 31st 1962, 1185 newborn infants have
been observed with one or more congenital malformations, i. e. with a frequency of 13,8°/°°. Distribution of this material in a first period of six years and in three subsequent quinquennia, and comparison of the frequencies of the subjects with malformations observed in the various periods allow us to draw the following conclusions:
1) in the period 1942-1962, especially in the latest years, the total frequency of congenital malformations has not exhibited significant variations;
2) the frequency of harelip and/or cleft-palate, omphalocele, hypospadia, polydactily, hypodactily and syndactily appears rather uniform. The same applies, as a whole, to CNS malformations, though a certain heterogeneity has been found in the frequencies of rachischisis observed in the various periods;
3 ) as for mongoloid, dysmyelitic and club-foot subjects a significant heterogeneity of the frequencies observed in the various quinquennia has been demonstrated.