when I was pregnant and on insulin, my dr. increased the insulin when my fasting blood sugar
began to go consistently over 95 in the mornings (if I was over 95 for 3 days, then we increased the nightime insulin. If my day time levels started to go out, then we increased the morning insulin). We increased by 2 units per increase, with close monitoring.
Your insulin requirement will increase during the pregnancy and it is normal to have to increase it.