Assessment of Prematurity by Birth Weight, Crown-Rump Length, and Head Circumference

Abstract

Measurements of occipitofrontal head circumference, crown-rump length and birth wt. were made on 119 living premature infants of 29-37 weeks'' gestation inclusive, and on 243 male and 209 female full-term infants. Crown-heel length was measured on 30 premature infants, and on 238 male and 206 female full-term infants. The mean and standard deviation for groups of increasing gestational age are presented, and the frequency distrs. and correlations for each measurement are given in the case of full-term infants. The criteria of prematurity were discussed. The following arbitrary measurements were found to fit the data sufficiently well to be of clinical value: head circumference less than 33 cm.,crown-rump length less than 32 cm., birth wt. 2500 g. or less. The proportion of misfits will be reduced by using 3 or more measurements in combination, together with gestational age. The correlations of birth wt. and crown-rump length to week of gestational age in premature infants were almost identical, viz, 0.61 and 0.60, resp. In 19 pairs of twins of like sex, the intra-class correlation of head circumference was 0.86; of crown-rump length, 0.79; and of birth wt., 0.80. In singleton premature infants of the same week of gestational age, the correlation between any 2 of the 3 measurements was approx. 0.80. In full-term infants, the highest correlation was found between crown-heel and crown-rump length, both of which correlated highly with wt. The correlations were smallest in the case of head circumference.