Infant head circumference growth is saltatory and coupled to length growth

Abstract

Background Rapid growth rates of head circumference and body size during infancy have been reported to predict developmental pathologies that emerge during childhood. Aims This study investigated whether growth in head circumference was concordant with growth in body length. Subjects Forty infants (16 males) were followed between the ages of 2 days and 21 months for durations ranging from 4 to 21 months (2616 measurements). Study design Longitudinal anthropometric measurements were assessed weekly (n = 12), semi-weekly (n = 24) and daily (n = 4) during home visits. Individual head circumference growth was investigated for the presence of saltatory patterns. Coincident analysis tested the null hypothesis that head growth was randomly coupled to length growth. Results Head circumference growth during infancy is saltatory ( p < 0.05), characterized by median increments of 0.20 cm (95% confidence interval, 0.10–0.30 cm) in 24-h, separated by intervals of no growth ranging from 1 to 21 days. Daily assessments identified that head growth saltations were coupled to length growth saltations within a median time frame of 2 days (interquartile 0–4, range 1–8 days). Assessed at semi-weekly and weekly intervals, an average 82% (SD 0.13) of head growth saltations was non-randomly concordant with length growth ( p ≤ 0.006). Conclusions Normal infant head circumference grows by intermittent, episodic saltations that are temporally coupled to growth in total body length by a process of integrated physiology that remains to be described.