Individual correction of birth weight for parental stature with special reference to small-for-date and large-for-date infants.

The aim of the present paper is to determine how parental stature measurements should be used to "correct" birth weight in order to improve the diagnosis of small or big-for dateness. A first approach, based on the pattern of coefficients of correlation between maternal and paternal weight and height, and birth weight (Tab. I), may be criticized for two reasons: 1) it does not take into account the possible variations of this pattern of correlations from one subcategory (for instance of age) of the sample to another and ii) it makes no difference between "genetic" and "environmental" components of parental influence on birth weight. A second approach takes into account the variations of parental stature measurements, of birth weight and of the pattern of correlations according to mother's age (Tabs. II and III). Briefly: The correlation between birth weight and mother's weight increases, the correlation between birth weight and father's weight decreases when mother's age increases (except for mother's older than 34), and these coefficents have the same value in the youngest group (mothers less than 21). These observations are consistent with the hypothesis of the predominance of the "genetic" component in the youngest group, which leads to the establishment of the coefficients to apply to each parental stature measurement by means of a multiple regression analysis carried out on this only group (Tab. IV). For the whole population, the correction must finally be calculated using the weights of parents at 20 years (or, if unknown, an approximate value). The correction is about ten grams per kilogram of mother's and eight grams per kilogramm of father's weight deviations from the mean values of the population to which they belong.