A contribution to the study of birth weight based on an Italian sample.

Abstract

SummaryBirth weight in relation to gestation time, maternal age, parity and survival has been studied in an Italian sample of 5486 single births. The results are compared with similar data on English births (Karn & Penrose, 1951). Italian babies are lighter at birth and have shorter gestation time (the correlation between birth weight and gestation time is 0·4), older maternal age and higher parity. The overall mortality is higher in the Italian sample (6·5%) than in the English (4·5%).Parabolas fitted to the logarithms of odds on survival for given birth weight and gestation time give maxima above the means. An alternative way of estimating birth weight and gestation time, associated with the lowest mortality, is given by the Z value (Penrose, 1955).The selective effect of the differential mortality with regard to birth weight and the problem of the measurement of natural selection in this case are discussed and a new formula is given for this measurement. Factors related to the rate of growth of the foetus are analysed and an attempt is made to give a better definition of ‘prematurity’ and of ‘postmaturity’.I wish to thank Prof. L. S. Penrose for his kind help and advice in the preparation of this paper. Thanks are also due to Miss Mary N. Karn for helping me in many ways and for drawing the graphs and diagrams.