I can't tell you what the odds are as I don't know what you are doinf differently this preganancy to last pregnancy and also because there are so many variables that change from pregnancy to pregnancy.

What I can tell is that your insulin needs start to increase from about 18 weeks onwards. This is when insulin resistance generally starts to set in so in all honesty you are really not going to get an accurate picture of how your pancreas is handling the stress until the 28 week test.

As for not getting a VBAC if you have GD again...personally I don't think GD on its own is a valid reason to deny a VBAC...plenty of women even those with full blown type 1 D achieve vaginal births and VBACs every day, in fact research is showing that such babies do better BSL wise after a vaginal birth than a caeser so I would be sticking to your guns on that one unless there are other issues come into play down the track.

If you follow a low GI diet from now on there is a good chance you may be able to minimise the effects of the insulin resistance by lowering your overall glucose load...after all less stress in the pancreas is less stress on the pancreas no matter where it comes from, and it certainly isnt going to hurt.

hugs from me and keep thinking those low BSL thoughts!!