A variety of iodine-containing cleansing agents or contrast dyes used in x-ray imaging tests can be given to the mother during pregnancy or to the baby after birth. Excess iodine can inhibit the production of thyroid hormone by the baby's thyroid. This is more likely to happen in small or premature babies. Likewise, medications given to the mother for Graves' disease, such as methimazole or PTU (see Chapters 11 and 13), can block the baby's thyroid from making thyroid hormone. Since the effects of excess iodine and antithyroid drugs disappear when they're no longer around, they cause only transient hypothyroidism.
Antibodies from the mother that block the effects of TSH on its receptor (see Chapter 1) can cause a very rare case of hypothyroidism in her baby. These antibodies are similar to the antibodies that cause Graves' disease by stimulating the TSH receptor, except that they have the opposite effect on the receptor. Since they've been present through much of the pregnancy, they may cause permanent deficiencies in brain development even though they gradually dissipate after birth.
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Once your pregnancy is over and done with, your baby is happily in your arms, and youre headed back home from the hospital, youll begin to realize that things have only just begun. Over the next few days, weeks, and months, youre going to increasingly notice that your entire life has changed in more ways than you could ever imagine.