Decreased leptin concentration in neonates is associated with enhanced postnatal growth during the first year

Leptin regulates maternal metabolism and fetal growth by reducing food intake and increasing energy expenditure, particularly during the third trimester. In this study, we investigated the relationships between leptin and growth, and explored the longitudinal change of leptin in early postnatal life. A total of 58 infants were categorized according to gestational length and birth weight. Arterial blood samples were taken within 24 hours (Day 1), and on Days 4 and 7 of life. Plasma leptin levels were measured by commercial human leptin enzyme immunometric assay. The average serum leptin level declined in the first week of life. There was a positive correlation between leptin level and body weight on Day 4. Neonates with leptin decrease between Day 1 and Day 4 had better weight gain at one year old, and the hospital stay day was shorter. Furthermore, the full feeding days and the duration of feeding priming and full feeding days in the leptin decrease group were less than in the leptin increase group. Serum leptin was significantly decreased and positively correlated with neonates' body weight gain in the first week of life. A rapid decline in serum leptin after birth is associated with greater future weight gain and physiological advantage for infants' life.