We measured the plasma leptin level in cord blood from infants who were large for gestational age (LGA) (n = 15), small for gestational age (SGA) (n = 16), and appropriate for gestational age (AGA) (n = 38). AGA infants (n = 120), who were exclusively breastfed, were also studied during their first 4 postnatal days in a cross-sectional method. One blood sample was collected before breastfeeding from each infant. Plasma leptin concentrations were determined by radioimmunoassay.Results
The median (range) concentration of leptin from cord blood was increased in LGA infants and decreased in SGA infants compared with the level in AGA infants. There was a positive correlation between the log of the plasma leptin level in cord blood and both the infant's birth weight (r = 0.76; n = 69) and the body mass index (r = 0.63; n = 69). The normal 3% to 6% weight reduction that occurs during the first 4 postnatal days was associated with a 26% decrease in the plasma leptin level in healthy breastfed infants.Conclusions
The plasma leptin level is highly correlated to the size of adipose tissue mass and decreases in connection with the initial physiological weight loss in newborn infants. These data provide evidence that leptin is highly related to the nutritional status already during the fetal and neonatal periods. Pediatrics 1998;101:429-432.