A mother's levels of thyroid hormone are crucial to help with brain development in a baby during pregnancy. The first trimester is particularly important, as that is the time frame before the fetal thyroid develops and starts producing its own hormone. While screening for thyroid disease is not a part of normal evaluation during early pregnancy, it has long been known that even mild hypothyroidism, or elevated thyroid antibodies can increase miscarriage risk.
Researchers looked at whether subclinical hypothyroidism and/or autoimmune thyroid disease during early pregnancy — the 4 to 8 week period — was also associated with higher rates of miscarriage.
The researchers evaluated more than 3,000 women in early pregnancy. They grouped the women according to the severity of their subclinical hypothyroidism, as well as presence of antibodies/autoimmune thyroid disease, and then compared the miscarriage rates.
The women were classified as:
- normal thyroid function
- subclinical hypothyroidism
- autoimmune thyroid disease
- subclinical hypothyroidism and autoimmune thyroid disease
Of the group, 3.5% had miscarriages before 20 weeks of gestation. The women who had subclinical hypothyroidism, autoimmune thyroid disease or both had the highest risks, compared to women with normal thyroid function.
Specifically, the women with both subclinical hypothyroidism and autoimmune thyroid disease not only had a higher risk, but also tended to have earlier miscariages.
What This Means for You?
While endocrinologists are not in agreement regarding treating women with normal thyroid function and thyroid antibodies, some studies have shown that treating these women may decrease the risk of miscarriage.
Integrative and holistic physicians have long recognized that thyroid hormone treatment may help those who have elevated thyroid antibodies (but “normal” reference ranges on TSH) by preventing progression to overt hypothyroidism. New research has confirmed this understanding.
This new research suggests that for women of childbearing age who have autoimmune thyroid disease – Hashimoto’s disease – and thyroid levels that fall within the reference range, thyroid hormone treatment may help reduce the risk of miscarriage.
Source: Liu H et al Maternal subclinical hypothyroidism, thyroid autoimmunity and the risk of miscarriage: a prospective cohort study. Thyroid. August 2, 2014