Correlates of lower leg length growth and weight gain in early life

Abstract

The aim was to examine how well short-term growth in lower leg length (LLL) and total body length are correlated with weight gain in early life in healthy infants. This is an observational study with weekly follow up for 2 to 13 weeks for ages between birth and 21 weeks. The study was done at the Mother's Choice Adoption Center, Hong Kong. Weekly measurement of lower leg length (LLL), total body length and weight were made in 22 healthy full term Hong Kong Chinese infants (12 boys and 10 girls). The sample represents all new infants coming to the adoption center during the reqruitment period, January to May 1994. The technical error of LLL was 0.53 mm, which corresponds to 20% of the weekly growth rate in early life. In comparison, the technical error for length was 2.8 mm, or around 40% of the mean weekly growth rate in length. The main finding was a significant correlation between the gain in LLL and weight for short-term growth in early life in normal healthy babies: over 2, 3 and 4 week intervals the correlation were 0.32, 0.40 and 0.51, respectively. On the other hand the correlation coefficients between the gain in length and in weight were much lower for intervals below 4 weeks. We conclude that LLL and not length can be recommended for short-term growth studies in early life for intervals shorter than 4 weeks; the shortest interval seems to be 2 weeks in normal children, but possibly shorter under catch up growth. For intervals of 4 weeks or longer no recommendation can be made at present. LLL measurements may be useful in nutritional, hormonal and/or metabolic studies in early life by adding reliable information about longitudinal bone growth.