Although a lack of a significant association between the circulating IL-6 levels and GDM has been observed in some studies [180,181,182,183,256], an elevated concentration of IL-6 has been frequently reported in GDM patients, even regardless of obesity [113,115,172,173,174,175,176,177,178,179]. This evidence concerns the gene IL6 and obesity due to melanocortin 4 receptor deficiency.