normally with a deficiency the doctor would give you a prescription for the proper amount that you're deficient in. before pregnancy, i was highly deficient in iron and doctors were astounded i was still able to move without fainting. i didnt ever finish my bottle dosage and two months after i stopped taking the medicine, my levels went up naturally due to increased blood flow from a surprise pregnancy! so my deficiency was completely healed due to baby in just a week! but anyway, when you do have a deficiency its specific to your body type and so id call the doctor just to be on the safe side regarding your pregnancy to see whats the safest dosage because some prenatals already have vit d. they know whats best for you and your changing body and all i can do is suggest the best i can