Cord blood leptin and IGF-I in relation to birth weight differences and head circumference in monozygotic twins

To investigate a potential role of leptin and insulin-like growth factor (IGF)-I on fetal growth and metabolic function we determined plasma leptin and IGF-I concentrations in twins in relation to discordant fetal growth.

In studying monochorionic twins with inter-twin birth weight difference, we investigated the relative contribution of genetic (fetus) versus environmental (maternal/placental) factors on growth. Thirty-six sets of twins (14 with discordant growth, birth weight difference >15%) who had been treated for severe twin-to-twin transfusion syndrome (TTTS) by laser coagulation were studied. Cord blood samples were collected at birth and analyzed for IGF-I and leptin. Inter-twin differences (delta) of birth weight and head circumference were correlated to delta hormone levels.

An inter-twin correlation for leptin (r = 0.69; p <0.0001) and delta IGF-I (r = 0.49; p <0.0001) was found. delta birth weight correlated significantly with delta IGF-I (r = 0.67; p <0.0001) but not with delta leptin (r = 0.23; p = 0.19). delta IGF-I concentrations did not correlate with delta leptin (r = 0.18). delta head circumference correlated significantly with delta leptin (r = 0.47; p <0.01) and with delta IGF-I (r = 0.46; p <0.01). Using a multiple regression model with head circumference as dependent variable, adjusted for gestational age, head circumference remained significantly associated with higher leptin concentrations in all patients (p = 0.03).

IGF-I is a good indicator for fetal growth and brain development. Leptin seems to be mainly genetically determined but may play a role in fetal brain development and is not only an index for fetal fat mass.