Published online by Cambridge University Press: 31 July 2008
It is generally thought that birthweight varies with the sex of the infant, gestational age and parity; there is, however, some controversy as to whether birthweight increases monotonically with parity. Further, some have suggested that maternal height and social class are also important, whilst earlier authors stressed the importance of genetic factors. This paper re-examines these relationships on the basis of an analysis of data on 6472 women who had a sequence of two or more singleton live births. The analysis shows first that the raw birthweights increase up to the fourth birth and that there are strong correlations between successive birthweights. However, when the birthweights are standardized for gestational age, maternal height, parity and sex, the relation between birthweight and parity almost disappears. On the other hand, the correlations between successive birthweights remain among the standardized scores, suggesting that there are other features specific to the mother which affect birthweight.