Weight Increments of Premature Infants. 135 



The increments thus determined were next compared with 

 those of fetuses of the same gestation age and with those of full- 

 term newborn children. 



The norm for fetal growth in weight was estimated from the 

 following empirical formulae: (1) F = 0.24 X 3 2 + 400, where F 

 is the body- weight in grams and X is the body length in cm., and 

 (2) F = 8.9 (X - 1) - 0.27 (X - i) 2 - 6.5, where Fis the body 

 length in cm. and X is the age in fetal or lunar months. The 

 norm for weight increment in the first nine postnatal months was 

 determined by calculation from 10 large series of published aver- 

 ages on the increase in body weight in the first year. When the 

 monthly weight increment rates of the premature infants are 

 compared with these norms it is found that they fall much closer 

 to the calculated rates of growth of fetuses of the same size and 

 age than to those of newborn children. This is shown particularly 

 well by group A of the smallest prematures which were approxi- 

 mately 7 fetal months old when born. The comparison is shown 

 graphically in the chart below. 



Fig. z. A graph showing monthly percentage increment in weight of a group 

 of premature infants ranging from i.o to 1.5 kg. in birth weight. The solid line 

 represents the rate of increment of the premature children in the first 9 months 

 after birth. The upper broken line represents the calculated rate of increment of 

 the fetuses of the same size and age as the prematures. The lower broken line 

 represents the rate of increment of full-term children. 



