Martha,a Patient Suffering from Hypothyroidism,has Just Found Out That She

Martha,a patient suffering from hypothyroidism,has just found out that she is pregnant.She contacts Dr.Hudson to find out whether she should continue her thyroid hormone replacement therapy during her pregnancy.Which of the following instructions is Dr.Hudson most likely to give Martha?

A) Discontinue treatment until the third trimester, when there is no longer a risk of the drug affecting fetal development.
B) Discontinue treatment because the thyroid hormones administered to pregnant women readily cross the placental barrier and affect fetal development.
C) Continue treatment as usual because the thyroid hormones administered to pregnant women do not readily cross the placental barrier to affect fetal development.
D) Continue the treatment at half the dosage as the growing fetus may be very sensitive to the effects of the drug.