In the linear mixed-effects models examining longitudinal changes in the hormonal levels from weeks 10–14 to 15–26, GDM was associated with significantly higher prolactin levels at weeks 10–14 (p = 0.01), but not the magnitude of change in prolactin levels from weeks 10–14 to 15–26 (p-interaction = 0.87). This evidence concerns the gene PRL and gestational diabetes.