That's why better go for morning checkup.

My wife used to go for morning checkup (light meal and no drinks) and was fine all along. Then one weekend, gynae was fully booked for morning sessions and so we went for afternoon checkup. That was when she was diagnosed diabetic (actually most pregnant women suffer temporary mild diabetic at some point of their pregnancy). Take the blood sugar test and she failed. We were advised to monitor food input and measure blood sugar after every meals. After 2 week or so, nah, just gave up and eat normally. The thing is it just took a bit longer for blood sugar to went down compared to their test requirement of 2 hours. We faked the blood sugar monitoring list to appease the gynae.