Children born small-for-gestational age: Postnatal growth and hormonal status

Abstract

It is generally recognized that children born small-for-gestational age (SGA) have a 5-7 times higher risk of short stature than children born at normal size. It has been suggested that the programming of the endocrine axes occurs during critical phases of fetal development and is affected by intrauterine growth retardation. This study was undertaken to characterize the postnatal growth pattern and the final height of children born SGA, as part of a population-based study (n = 3650), from birth to final height, and to evaluate the hormonal status in another group of prepubertal children born SGA (n = 134) without postnatal catch-up growth. The majority (88%) of 'healthy' full-term singleton SGA infants achieved catch-up growth during the first 2 years of life, and most of the increase in height occurred by 2 months of age. The SGA children who remained short at 2 years of age had a higher risk of short stature later in life. The risk of having a short final height (< -2 SDS) was five times higher for children with a low birth weight and seven times higher for those with a low birth length in comparison with children with a normal birth size. Moreover, about 20% of all children of short stature were born SGA. As a group, children born SGA will have a final height, expressed in SDS, as they had during the prepubertal years. This is in contrast to children, who became short postnatally. During puberty, these short children will have a mean height gain of 0.6 SDS for girls and 0.7 SDS for boys. The mean estimated secretion rate for growth hormone (GH) was lower in the short children born SGA compared with the reference groups born at an appropriate size for gestational age, of either short (p < 0.05) or normal stature (p < 0.001). Moreover, in the youngest children born SGA (2-6 years of age) a different pattern of GH secretion was found, with a high basal GH level, low peak amplitude, and high peak frequency. The majority of the children born SGA had levels of GH-binding protein within the range previously reported for normal children. However, the levels of insulin-like growth factor I (IGF-I), IGF-binding protein-3 (IGFBP-3) and leptin were significantly reduced compared with the reference values (p < 0.001, p < 0.01 and p < 0.001, respectively). In conclusion, the low spontaneous GH secretion rate and a disturbed GH secretion pattern, together with low serum levels of IGF-I, IGFBP-3 and leptin, might contribute to the reduced postnatal growth in some of the subgroup of children born SGA who remained short during childhood.