This study will evaluate the relationship between structured nutrition counseling, diet quality, and advanced glycation end products in pregnant women with gestational diabetes mellitus and women with normal glucose tolerance. Participants will be assigned to either a structured nutrition counseling group or a standard care group according to glucose tolerance status. The counseling program will include education and follow-up on healthy eating during pregnancy, gestational diabetes management, portion control, food choices, meal planning, and cooking methods. Diet quality, dietary habits, biochemical parameters, advanced glycation end products, gestational weight gain, and fetal outcomes will be assessed during follow-up.