Associations Between Maternal and Cord Blood Leptin Levels and Anthropometry of Mothers and Infants

Background/Objectives: As birth weight is related to later obesity risk, its associations with maternal pre-pregnancy body mass index (BMI) and leptin values in serum during pregnancy are of interest for obesity prevention. This study aimed to describe the association of leptin levels in maternal circulation and cord blood as well as pre-pregnancy BMI (pBMI) with infant anthropometry at birth and until the age of four months. Methods: Data on maternal pBMI, at delivery and four months after birth, and on infant weight and length at delivery and at age four months were collected in an observational study in Bangkok, Thailand. In a subgroup of 38 mother–infant dyads, leptin was measured in maternal blood serum at delivery and infant age 4 months and in cord and infant serum at 4 months. Associations were tested with correlation and multiple linear regression analyses in this explorative study. Results: The maternal serum leptin was 32.4 ± 17.8 ng/mL at delivery and 11.1 ± 8.9 ng/mL at four months (p < 0.001 for difference) and correlated (r = 0.45). Cord serum leptin was significantly higher in female than male infants (17.5 ± 9.8 ng/mL vs. 7.7 ± 4.9 ng/mL, p < 0.05) and not related to infant leptin at age four months. There was no significant association between maternal and cord serum leptin levels. Birth weight was strongly associated with pBMI (standardized β = 0.77, p < 0.001) and inversely related to maternal delivery leptin levels (standardized β = −0.44, p = 0.008), while the association with cord serum leptin was not significant. Conclusions: Our findings indicate that pBMI is strongly related to birth weight, while higher maternal leptin concentrations were independently associated with lower birth weight after accounting for pBMI. Cord serum leptin did not significantly correlate with maternal leptin levels and only tended to be positively associated with birth weight.