I had gestational while pregnant, diagnosed after 3 hour test, with no known cfrd before pregnancy. My inexperienced with cf OB had me try doing a regular low carb diet and I started to lose weight after only a week or 2 and my sugar was still high so I had to start insulin and by that time my pulm dr stepped in and told me NOT to eliminate carbs and therefore I was taught to carb count so I could still eat whatever I wanted.
It was very scary and nerve racking learning to give my self a shot, it's not easy at first, especially when it has to go into your pregnant belly. I remember crying the first few times because I was about 26 weeks pregnant and I could feel my daughter moving and kicking my hand while I'm trying to stick this needle in my belly.
Unfortunately as much as I thought and hoped the diabetes was going to be over once I delivered, it didn't go away. Now 5 years later I still need insulin just about with everything I eat, but it is much easier to manage now especially with my pump.
Good luck, if you end up needing insulin, chances are it will only be temporary. I think I was just unlucky as usual. If you have any questions feel free to message me!