PZ - just google gestational diabetes dietary plan or something like that or have a look in the GD chatter thread.

Basically avoid having too much carbs eg. you wouldn't have toast for brekkie, a sandwich for lunch and pasta for dinner.

Good things for brekkie - a low GI cereal (Special K was recommended), porridge (proper porridge not the sachets that you add milk/water to that are full of sugar)
Good things for lunch - turkey breast sandwich with salad/coleslaw. Or any other sort of meat/fish/salad combo. Avoid too much mayo and coleslaw dressing.
Good snacks - celery with peanut butter.
Good things for dinner - meat and veggies (go easy on the potatoes or swap to sweet potato), dim sums with coleslaw (again, easy on the dressing), wholemeal pasta, wholemeal rice.

I had to be really strict and couldn't even eat wholemeal pasta or rice but given that you just being cautious, you wouldn't need to be anywhere near that strict.

But like I said, google a diet plan. I found it easier to just have a look at meals I could eat rather than see what things were low GI and then have to work out the meals myself.

Oh, and my diabetes educator told me to stick to Burgen bread. Even the bread that calls itself wholemeal often isn't that good. Definitely don't eat white bread.