I had no symptoms it came up as positive in my blood tests. Gest diabetes can cause babies to be larger than normal (or in my case smaller than normal) you can have too much weight on yourself as well. I didn’t have to go on injections I just had to take the pills (can’t remember the name) I had to monitor my blood sugar levels and change my diet. I actually lost 20 kilos with the changes and my son was born healthy and the diabetes disappeared pretty much straight after birth

Pretty sure blood tests show gestational diabetes before any symptoms appear, which is good