Not a personal experience of mine but when I was teaching in WA the local Imams daughter was in my class. While discussing her needs for fasting while at school he mentioned his wife was pregnant and was only fasting for two weeks that year due to the pregnancy (I think there were other factors playing into that as well). I am assuming based on what he said it is possible to do things a differently while pregnant? I'm not 100% sure though. Anyway I hope you go ok and are able to get plenty of rest especially since your teaching. That alone can tire you easily without the added demands of fasting .