Serapio S, et al. - Researchers intended to determine if there is an association between maternal leptin levels with maternal obesity, gestational weight gain (GWG), single nucleotide polymorphisms (SNPs) within the leptin gene, and the age-adjusted birth weight of the child. Maternal leptin levels (n = 740) and SNPs (n = 504) were analyzed in blood samples taken during pregnancy weeks 16–19 in the Uppsala Biobank of Pregnant women. The best positive explanatory factor for maternal leptin levels has been identified as maternal BMI. For GWG, leptin was a strong positive explanatory factor. Nevertheless, the birth weight of uncomplicated pregnancy children depended on maternal height, BMI, GWG, and parity but not leptin levels, except in morbidly obese women where there was a negative connection between maternal leptin and birth weight. The authors believe that this suggests a modified placental function, which is not reflected in the complication of pregnancy. Overall, they concluded that maternal leptin levels have no greater impact on the child's birth weight than BMI, GWG, and parity.