A: Untreated thyroid conditions can cause problems during pregnancy, but most women who are properly treated go on to have healthy pregnancies and babies. The thyroid is a gland located in your neck that produces a hormone responsible for regulating your metabolism and controlling many of your body's organs. Thyroid disease happens when your immune system mistakenly attacks and destroys cells in the thyroid gland. This results in your thyroid producing either too many hormones (hyperthyroidism) or too few (hypothyroidism). Some women develop thyroid problems before they become pregnant, while others experience them for the first time during pregnancy.
If you have hypothyroidism, your baby has a higher risk of neurological or developmental problems (like lower IQ). You'll be given hormone replacement pills to boost the level of thyroid hormone in your blood. If you have hyperthyroidism, you're more likely to develop a type of pregnancy-related high blood pressure called preeclampsia, and you'll need medication to reduce the amount of thyroid hormone your body makes. However, you should not be given radioactive iodine (a common treatment) during pregnancy because it can damage your unborn baby's thyroid gland.