Short-term growth in head circumference and its relationship with supine length in healthy infants

Background: Daily changes in height have been found to be a non-linear process. Its exact pattern is still controversial. In previous studies on 34 healthy children aged 0.32-12.99 years, we found that growth is a tri-phasic process: stasis, steep changes (or saltation) and continuous growth. There is very little information in the literature about daily changes in head circumference. Aim: The present study analysed growth in head circumference and supine length in eight healthy infants. Subject and methods: Supine length and head circumference was measured five times a week during 151 days. Mean intra-observer technical error of measurement (TEM) for head circumference and supine length were 0.10 and 0.15 cm, respectively; smoothing techniques used were based on the TEM with a hard rejection criterion. Results: The three types of events previously found in supine length are also present in head circumference. The number of steep changes was greater in supine length than in head circumference. Conclusion: Growth is a discontinuous and irregular process, present not only in long bones but also in skull bones. Although long-term growth curves of head circumference and supine length are different, when measured on a daily basis findings suggest that skull and long bones have a common pattern; the physiological basis needs future research.