Individual variability in height tracking in infancy: comparison of two longitudinal data sets of children born in 1990 and 1996 in Vilnius, Lithuania.

Abstract

The aim of this study was to investigate variability of individual trajectories for height in two different birth cohorts of Lithuanian infants. Data were derived from the personal health records of 781 (399 boys and 382 girls) and 263 (139 boys and 124 girls) children born in 1990 and 1996 (respectively) in the city of Vilnius in Lithuania. The height of each child at birth, at one year and two years of age was investigated. The analysis of growth tracking was performed tracing the main centiles for height (3, 10, 25, 50, 75, 90 and 97). According to increase of height along the main centiles, five types of growth curves were possible. The average number of changed centile tracks for height for girls born in 1990, girls born in 1996 and boys born in 1996 was 2.05 ± 1.12, 2.02 ± 1.25 and 2.03 ± 1.06, respectively. However, the average number of changed centile tracks for height for boys born in 1990 was 1.74 ± 1.16, which differed significantly (p < 0.001) from the average number of changed centile tracks for height for girls born in 1990 and 1996, and boys born in 1996. Statistically significant differences (p < 0.001) were obtained between the incidences of the stable type of growth curve: the boys born in 1996 have presented the aforementioned type of growth curve much rarer compared to both the girls born in the same year and the boys born in 1990.