GD has nothing to do with diet or how healthy you eat. It's about hormones and your placenta, its just luck of the draw as to if you develop it in pregnancy. If you have GD then you'll be advised to follow a low carb, low sugar diet that is high in protein and natural fats. You'll then have to test your blood sugar levels 4 times a day to ensure what you're eating is keeping you within the normal sugar levels. This would all be explained to you though by your midwife, including the potential risks it can present for birth and how it can be managed through meds or insulin if not able to be managed through diet.
Like those above said - it you have GD its not your fault I literally cried for a week when I was diagnosed with it. Lots of guilt and blaming my size. It wasn't until I educated myself and spoke to diabetes midwifes/consultant' that I learned that it wasn't. There is lots of ignorance around GD - i found that unless midwives/nurses were specialised in GD there was alot of misinformation and silly comments. - like a midwife telling me it's all the sugar and processed food id been eating. - which was cheeky as because though I'm overweight my diet isn't actually that bad. I hope you don't have it, but if you do don't worry!x
Please know GD has everything g to do with your placenta!!!! Your placenta gives off a hormone called HPL and that can cause insulin resistance. It has nothing to do with your eating habits. I had GD with my son and this is what the nutritionist told me! I stuck with high protein meals and I would take a walk after eating. I never needed to add medication like insulin injections or metformin, and we managed❤️