What are the most common causes of hypothyroidism during pregnancy?
Overall, the most common cause of hypothyroidism is the autoimmune disorder known as Hashimoto’s thyroiditis (see Hypothyroidism brochure). Hypothyroidism can occur during pregnancy due to the initial presentation of Hashimoto’s thyroiditis, inadequate treatment of a woman already known to have hypothyroidism from a variety of causes, or over-treatment of a hyperthyroid woman with anti-thyroid medications. Approximately, 2.5% of women will have a slightly elevated TSH of greater than 6 and 0.4% will have a TSH greater than 10 during pregnancy. What are the risks of hypothyroidism to the mother? Untreated, or inadequately treated, hypothyroidism has been associated with maternal anemia (low red blood cell count), myopathy (muscle pain, weakness), congestive heart failure, pre-eclampsia, placental abnormalities, low birth weight infants, and postpartum hemorrhage (bleeding). These complications are more likely to occur in women with severe hypothyroidism. Most women with mild hypothyroid
