Among the recognized causes of recurrent miscarriages are undiagnosed or poorly controlled health conditions in the mother. Undiagnosed thyroid disease is one such problem linked to miscarriage in some studies. Given that the symptoms of thyroid disease are often less than obvious, many women suffering recurrent miscarriages wonder whether they too might have an untreated thyroid condition.
But "thyroid disease" is actually category of different problems rather than a single entity. What kinds of thyroid conditions might be a factor miscarriages? There's a lot of mixed information out there. Here's what UpToDate, an online reference site for doctors and patients, has to say:
"Some studies have reported an increased rate of fetal loss in women with high serum thyroid antibody concentrations (thyroid peroxidase or thyroglobulin), including those who are euthyroid. Thyroid autoimmunity has also been related to unexplained infertility and implantation failure. Direct evidence of causality, however, is still lacking and conflicting data have also been reported.
Poorly controlled thyroid disease (hypo- or hyper-thyroidism) is associated with infertility and pregnancy loss. Excess thyroid hormone increases the risk of miscarriage independent of maternal metabolic dysfunction."
So, it's unclear what thyroid antibodies (antibodies against thyroid proteins) mean in terms of miscarriage. Some studies suggest women with thyroid antibodies have a higher risk of miscarriage or infertility even when their hormone levels are normal, but the evidence is mixed, and right now there's not enough information to say whether thyroid antibodies are directly related to the miscarriages in such cases. If you're at risk for thyroid disease, your doctor will probably look more closely at your thyroid hormone levels. Uncontrolled hyperthyroidism and hypothyroidism do appear to be linked with miscarriages, and because these conditions can be treated with medication, it's worth consulting a doctor if you think you might be at risk.
Here are some questions you might have about thyroid conditions and other causes of recurrent miscarriages.
How do I know if I might be at risk for thyroid disease?
If you feel you have symptoms of hypothyroidism or symptoms of hyperthyroidism, ask your doctor about testing. The testing process usually consists of simple blood tests.
How are thyroid diseases treated?
The treatment varies by the condition, but usually treatment for hypo or hyperthyroidism consists of medication to replace thyroid hormones or reduce excess hormone levels, respectively. The medications are safe during pregnancy.
If it turns out I have thyroid disease, does that mean it caused the miscarriage?
It's impossible to say. There's usually no way to know what caused a past miscarriage unless testing was done at the time of the loss. If you do have a thyroid problem, however, it's a good idea to get the condition under control before you get pregnant again.
What other chronic diseases are linked to miscarriage?
Uncontrolled diabetes, kidney disease, and lupus are a few examples of chronic diseases that might mean a higher risk of miscarriage when not managed. But normally, moms who have those diseases have other symptoms -- miscarriages aren't usually the first sign that there's a problem (but see your doctor if you think you have other symptoms). There's some suspicion that undetected celiac disease might play a role in recurrent miscarriages, but no proof at this time. Antiphospholipid syndrome is a usually silent condition that is found in about 15% of women with recurrent miscarriages, and chances are that your doctor will recommend testing for antiphospholipid antibodies if you have had three or more miscarriages.
Want to learn more? See UpToDate's topic, "Definition and etiology of recurrent pregnancy loss," for additional in-depth medical information.
Tulandi, Togas and Haya M. Al-Fozan. "Definition and etiology of recurrent pregnancy loss." UpToDate. Accessed: June 2010.