An update of the Swedish reference standards for weight, length, and head circumference at birth, for each week of gestational age, is presented. It is based on the total Swedish cohorts of infants born 1977-1981 (n = 475,588). A "healthy population" (79%) was extracted, using prospectively collected data. Weekly (28-42 weeks) grouped data for length and head circumference were well approximated by the normal distribution, but the distributions for birthweight were positively skewed. The original skewed distributions for birthweight were transformed, using the square root, resulting in distributions close to the Gaussian. For smoothing purposes, the weakly values for the mean and the standard deviation were both fitted by a third degree polynomial function. These functions also make possible the calculation of the continuous variable, standard deviation score, for individual newborn infants as well as a comparison of distributions between groups of infants. The reference values and charts presented here have two major advantages over the current Swedish ones: the sample size used is now sufficiently large at the lower gestational ages, so that empirically found variations can be used, and the skewness of the birth weight distribution has been taken into account. The use of the reference standards presented here improves and facilitates evaluation of size deviation at birth.

No abstract

According to the "ICP-growth model" (ICP = Infancy, Childhood and Puberty components), linear growth during the first three years of life can be represented mathematically by a combination of a sharply decelerating Infancy component and a slowly decelerating Childhood component. Growth as measured by supine length is analysed for 191 longitudinally followed healthy infants using this model. The main aim is to devise ICP-based methods for biological and clinical applications. The onset of the Childhood component, which occurs some time between 6 and 12 months of age and is typically abrupt, can be detected on an individual basis. Its starting point probably defines the as yet unknown age at which growth hormone begins to exert a significant influence. The analyses have also revealed some new facets of linear growth. Most infants are found to have a non-linear decelerating Infancy component, free from seasonal influence. Age at onset of the Childhood component is earlier for girls than for boys and is positively related to the magnitude of the Infancy component. During the second year of life the variation in growth rate of the cohort increases. This fluctuation is found to be seasonal and greater for those with late onset of the Childhood component. During the third year of life the growth pattern is stabilized.

No abstract

Analysis of linear growth using a mathematical model. 11. From 3 to 21 years of age. Acta Paediatr Scand [Suppl] 337:12, 1987.