Provided that you are carrying only a singleton and have otherwise been eating healthy, I don't see that intermittent fasting would be a problem unless it negatively affects your BG or you've been having vomiting issues. The idea that you have to have this continual input of food is a modern one. Not done in much of the world or pre-1950 US (two meals a day with maybe a snack) . In fact, doctors have been pushing excessive weight gain for years; they are starting to backpedal on that now.
I'd still fly it by your doctor, but I personally don't think it's unwise if you are healthy and young. If you are over 35? Not so much.
I only ate two meals a day for the latter 1/3 of my pregnancy because I had no appetite and had a lot of nausea. So long as my 2 meals and snack had plenty of protein, diary, fruits and vegetables, doctor wasn't concerned. However, I did not have GD.