A1C test for gestational diabetes??

I failed my one hour glucose test.. Went to take the three hour and about an hour into it I threw the drink back up! Since I'm so far along they won't make me retake it. But they did draw my blood again for my A1C for the last three months. They're going to diagnose me or not for GD based on those results. Has anyone else had to do this?? I've never heard of that before.