I'm a bit flumaxed by how you've been told to test...
You need to be testing before and after the same meal to get a idea what's happening, you can't compare a BG taken before a meal, and then compare the BG from the corrosponding meal the following day.. Too many varibles to really make this useful information :?
Not sure at what stage of pregnancy, but they will monitor you closely to see what is happen with your blood glucose levels, as they might need to introduce medication to maintain control it will depend really how your body is reacting to the stresses and strains of the pregnancy, as some just need to alter their diet, cut out sugar be carefull on carbs and types they eat needing no other treatment, but then some find that they need medication in my day it was insulin but now that may have well changed..
Hope this helps..