Decrease of thyroid antibodies during pregnancy.

The behavior of serum anti-thyroglobulin (Abs-Tg) and antimicrosomal antibodies (Abs-Mc) was examined during and after normal pregnancies. The antibodies titer decreases as pregnancy progresses; they cross the placenta and are present in the fetal serum. Infants' thyroid function is not affected by this transplacentar transfer.