Mortality in the first week of life and mode of delivery

11 923 singletons with birthweight greater than 775 g born consecutively at the 2nd School of Medicine of Naples during a four-year period (November 1975 to October 1979) were the subjects of the study. Mortality in the first week of life was 10.9, 9.7, 6.7 and 10.7 per 1 000 respectively in the four years. The total variability of the crude death rates was reduced by 21.4% after standardization for birthweight distribution alone and by 28.6% when both birthweight and mode of delivery were taken into account. Therefore only a small fraction of the variations in mortality can be ascribed to changes in the distribution of modes of delivery during the study period. Most of these variations are probably related to the quality of perinatal care, which seems to have improved only for babies under 1 526 g. Birthweight specific mortality in relation to mode of delivery is further discussed.