This study was designed to examine the effects of adiponectin, leptin, insulin, insulin-like growth factor (IGF)-I and IGF binding protein (BP)-3 levels in cord blood on weight, length, and adiposity at birth in healthy term infants. In addition, we evaluated the mechanism to change the hormone levels in appropriate for gestational age (AGA) during the first month.

We collected cord blood from 200 term neonates (109 males, 91 females) with no perinatal problems, and measured the hormone levels and anthropometric parameters including weight, length, and skin-fold thickness. Term neonates were divided into 3 groups as follows: birth weight appropriate for gestational age (AGA) (n=132), birth weight less for gestational age (SGA) (n=29), and birth weight more for gestational age (LGA) (n=39). Venous blood samples of 15 fullterm healthy neonates were obtained at 3, 7, and 30 d after birth.

The adiponectin, insulin, and IGF-I levels were significantly lower in the SGA group than in the AGA and LGA groups. The leptin levels were significantly higher in the LGA group than in the AGA and SGA groups. Cord blood adiponectin, leptin, insulin, IGF-I, and IGFBP-3 levels correlated significantly and positively with birth weight and the sum of the skin-fold thickness. A significant positive correlation was observed between adiponectin, leptin, and IGF-I levels and birth weight. Adiponectin level correlated significantly with that leptin level (r=0.191, P =0.038), but not with insulin, IGF-I and IGFBP-3 levels. IGF-I levels were higher in females than in males. At 7 d after birth, the leptin level decreased along with physiologic weight loss, and then increased. IGF-I, also decreased at 3 d, significantly increased 1 month later.

We suggest that adiponectin, leptin, insulin, IGF-I, and IGFBP-3 play an important role in regulating fetal growth. Adiponectin may be involved in regulating fetal growth through mechanisms different from those mediated by insulin or IGF-I. High levels of IGF-I in female neonates indicates a gender difference which serves as evidence for in utero sexual dimorphism. It is likely that IGF-I has a more important role than that of hormones in postnatal growth.