Background Head growth and anterior fontanel (AP) closureare passive processes in response to brain growth. The growthof the brain and skull starts in the third week of intrauterinegestation. roth processes run simultaneously as a part of integralgrowth, along 'With increasing gestational age, until post􀀿birth.Measurement of head circumference (He) and AF in newbornsis done to determine if the brain and skull grew normally duringthe intrauterine period.Objectives To investigate the differences in He and AF sizebetween preterm and full􀀿term infants, and the relationshipbetween gestational age (GA) and birth weight (BW) to Heand AF size.Methods This was a descriptive analytic study on preterm andfull􀀿term newborns. Measurement of HC and AF was conductedin three phases: just after birth, 1x24 and 2x24 hours of age.Analysis of HC and AF size differences between preterm and fullterm subjects was performed, as well as analysis of the correlationbetween GA and BW to HC and AF size.Results Two hundred fifty newborns completed the study. Therewere 180 full􀀿term and 70 preterm subjects. Median HC in full􀀿term and preterm male subjects were 34 cm (range 31􀀿37 cm)and 31 cm (27􀀿34 cm), respectively. Median HC in full􀀿termand preterm female subjects were 33 cm (31􀀿36 cm) and 32 cm(27􀀿3S.S cm), respectively. Median AF in full􀀿term and pretermmale subjects were 2.17 cm (1.0SA.6 cm) and 2.22 cm (1.3SA.Scm), respectively, and in full􀀿term and preterm female subjectswere 2.02 cm (lA.1S cm) and 2.22 cm (0.7SA cm), respectively.The HC of preterms were significantly lower than the fullterms(P