Some midwives allow you to drink a measured qty of juice instead of the glucola for the 1 hour test. So absolutely, consuming a large amount of carbs with no protein before the test could throw off your results. You basically had 2-3 times the sugar they think you had, and your body was busy processing that.
Before my 1 hour with my first son I had cereal with milk. Failed the 1-hour by about 5 points, passed the 3 hour (fasting) with flying colors.
With my second son, I drank juice instead of glucola. Sugar quantity was the same, but I figure since I never ever drink soda, this would be a more accurate measurement of how my body processes the sugars it actually consumes, as opposed to sugar in a form it would never come in contact with. My midwife agreed. I passed that test.
This time, my midwives (different group, since I've moved) also allowed a meal-based 1 hour glucose test. I just took that on Wednesday, so I don't know if I passed or not yet. But, all I had for breakfast before that was eggs.
Honestly, I'd ask for a redo on the 1 hour test before taking the 3 hour. Just read the label on the juice you drank... you're supposed to have 50g sugar for the 1 hour test. How much extra did you get from the juice alone, nevermind the pizza?
Also, only eat protein before the test. It helps stabilize your blood sugar. In general, it's a good idea to eat protein before overindulging on carbs anyway.
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