Your doctor knows more about the prescription than you do, do not worry. I am also pregnant and taking 400mg a day. Normally women's prog. Level is much higher and that is why they should not take a supplement. In our case, it is very low and we need this supplement to make up for what our body is not producing. Talk to your doctor about it, but in the meantime let your mind be at ease. Many women in our situation are prescribed this medication.