A comparison of the mid-arm circumference/head circumference ratio and ponderal index for the evaluation of newborn infants after abnormal intrauterine growth.

We studied the accuracy of the ponderal index and the mid-arm circumference/head circumference ratio for detecting newborn infants who were likely to be symptomatic because of aberrant intrauterine growth. Sixty infants were evaluated because of suspected intrauterine growth retardation; both the mean ponderal index and mid-arm circumference/head circumference ratio were significantly lower in the group of 30 symptomatic infants than in the group of 30 asymptomatic infants (p less than 0.05). However, the mid-arm circumference/head circumference ratio identified a significantly higher percentage of the symptomatic infants than the ponderal index (80% vs. 47%; p = 0.007). An additional 60 infants were evaluated because of suspected abnormal intrauterine growth acceleration. The mean mid-arm circumference/head circumference ratio, but not the ponderal index, was significantly higher in the group of 30 symptomatic infants than in the group of 30 asymptomatic infants (p less than 0.005). Again, the mid-arm circumference/head circumference ratio identified a significantly higher percentage of the symptomatic infants than the ponderal index (79% vs. 33%; p less than 0.001). The mid-arm circumference/head circumference ratio is more accurate than the ponderal index for the evaluation of potentially symptomatic newborn infants who suffered abnormal fetal growth. The ponderal index is not useful for the detection of symptomatic large-for-dates infants.