Background Head circumference (HC) is measured in newborns to evaluate head growth. It is not known, whether HC is always an appropriate measure of head volume (HV). Digital capture of the neonatal head offers information on HC and HV.

Aims To determine

1. overall correlation of HC and HV and

2. with regard to postmenstrual age (PMA) and

3. with regard to the actual body weight (BW).

Methods Head measurements with STARscanner laser shape digitizer (Vorum research Corp., Vancouver, BC) were performed in preterm infants prior to discharge over a 12 month period. Data on HC and HV were calculated with STARscanner Laser Data Acquisiton System (Orthomerica, Orlando, FL) and analyzed in different subgroups.

Results Included were 243 neonates at time of discharge (mean HC 32.8±1.9 cm, mean HV 356.7±64.3 ml). a) There was an overall correlation between HC and HV (r=0.90, R²=0.81, p<0.001). Correlation between HC and HV was: b) in infants with a PMA < 37 (r= 0.71, R²=0.52, p=0.001) vs. PMA > 37 weeks (r=0.92, R²=0.85, p<0.001) and c) in BW < 2500g (r=0.69, R²= 0.49, p=0.04) vs. BW >2500g (r=0.88, R²=0.77, p<0.001).

Conclusions Neonates with comparable HC can show very different HV, especially in infants with low PMA or BW. Thus additional measurement of HV enables to detect variable patterns of head growth and shape. Underlying causes and the meaning for neurological outcome need to be determined.