However, despite the recognized importance of serotonin metabolism in gestation, the specific impact of maternal obesity and overweight conditions on placental serotonin gene expression remained inadequately defined until now. A pivotal aspect of this study was the consideration of maternal glucose tolerance status—specifically distinguishing between normal glucose tolerance (NGT) and gestational diabetes mellitus (GDM). The researchers hypothesized that glucose intolerance might interact with maternal BMI to influence placental serotonin-related gene expression in a synergistic or moderating manner. Furthermore, the study indicated that glucose tolerance status exerts a moderating effect on the relationship between maternal BMI and serotonin gene expression. Placental expression of the serotonin transporter (SERT) gene: associations with maternal overweight/obesity and neonatal anthropometry.