SEX-DIFFERENCES IN WEIGHT IN INFANCY AND THE BRITISH 1990 NATIONAL GROWTH STANDARDS

Objectives-To determine if there is a sex difference in infancy in the new British national standards for weight (based on data from 1990). Design-Weight data in a birth cohort were compared with the 1990 stand ards and Tanner and Whitehouse (1966) standards up to age 12 months. S etting-Newcastle upon Tyne. Subjects-3418 term infants. Results-Our co hort showed a mean difference in standard deviation scores of 0.42 bet ween boys and girls (P<0.0001) when compared with the 1990 standards. Two and a half times as many girls as boys had weights below the 3rd c entile during the first year, with an equivalent excess of boys above the 97th centile (P<0.0001). Similar results were found with Tanner an d Whitehouse standards. Conclusions-These differences could result in substantial sex bias in the identification of poor growth in early chi ldhood. The standards need modification.