It all breaks down to simple sugars. Same thing
in your digestive tract. Pasta, bread, etc. It will elevate your
blood sugar. There is no doubt about it.
As much as you want to "just make it by" and not get stuck with a gestational diabetes diagnosis, if you have it, you want to know so that you can minimize the complications associated with it.
Eating the night before or that morning shouldn't make much of a difference. But obviously it can make some difference.