To the Editor:—The painstakingly collected data on physical measurements in premature infants presented by Drs. Woolley and Valdecanos in their article Growth of Premature Infants in the May issue of the American Journal of Diseases of Children provides an excellent illustration of what I feel is an important conceptualization in regard to prematurity.
In the course of gathering information on approximately 4,700 premature infants born in Maryland in 1952, we constructed a regression equation relating birthweight to length of gestation. This equation assigns roughly 1 month of prematurity for the 4 to 5 lb. weight group, 2 months for the 3 to 4 lb. group, and 2.5 months for the 2 to 3 lb. group. When these corrections are applied to the data given by Dr. Woolley for the 3 birthweight groups, it is apparent from the Figure that all of the weights fall on a curve which parallels