Hashimoto’s thyroiditis is a chronic inflammatory autoimmune disease where various antibodies are mistakenly directed against healthy thyroid tissue, resulting in a destruction of these cells and consequent reduction in thyroid hormone levels (hypothyroidism). Health Central states that women are roughly twenty times more likely than men to be diagnosed with this condition. Given the potential for complications during pregnancy and the prevalence of Hashimoto’s in the female population, it is important that these hypothyroid patients acquaint themselves with some of the more common problems surrounding childbirth.
What are the possible pregnancy complications from my Hashimoto’s disease?
When a woman carrying this diagnosis becomes pregnant, there are certain possible problems that may arise over the course of her pregnancy, particularly when she is without active treatment for the condition. Such problems may affect mother, fetus or both. Fortunately, careful compliance with medications and regular testing can significantly reduce the likelihood of such instances, but one must remain cognizant of such potentialities regardless.
Among the most common complications arising from overt hypothyroidism during pregnancy are preeclampsia/hypertension, placental rupture, preterm delivery with low birth weight, postpartum hemorrhage, and physical/neurological/psychological problems for the child. Indeed, as noted by the Mayo Clinic, “Babies born to women with untreated hypothyroidism due to Hashimoto’s disease may have a higher risk of birth defects than do babies born to healthy mothers.”
What complications might arise if my medication dose is too high or too low?
When thyroid medication (thyroxine) dosages are not adjusted properly, the resulting complications may be those of either hyperthyroidism (meds too high) or hypothyroidism (too low). So any complications seen in these circumstances would most likely be those of the respective thyroid state the patient finds herself in. For those on too little medication, these will include all of the scenarios mentioned above, while those on too much medication – and therefore thrown into a hyperthyroid state – are at increased risk for premature labor, miscarriage, stillbirth and heart failure, in addition to preeclampsia and low birth weight as above.
What if the initial onset of Hashimoto’s occurs during pregnancy, and my doctor checks my TSH, which is in a normal range for most labs (.5 – 6.0), but too high for an endocrinologist’s range (.3 – 3.0), and thus my hypothyroidism is undetected and untreated during pregnancy?
Virtually all women, including those without thyroid conditions, experience a mild hypothyroidism of pregnancy, driven by the increased maternal-fetal demand during this special state. Therefore, reduced hormone levels on their own without confirmation of antibodies are not necessarily abnormal over this period (though they should still be addressed and treated). That being said, there is a difference between this expected state and true hypothyroidism, of any variety, requiring additional attention. According to Medscape, “Patients who are diagnosed with Hashimoto thyroiditis or hypothyroidism from any cause during pregnancy should be started on a levothyroxine dose close to their replacement requirement, and the TSH level should be normalized as soon as possible. Untreated hypothyroidism carries increased maternal and fetal complications.”
The good news is that lab results falling within the old, but outside the new, parameters will mainly detect very mild and possibly asymptomatic (“sub-clinical”) disease, which as indicated above, can then be easily treated with medication to restore hormone levels to normal. This means that a patient who finds herself in this situation can be somewhat reassured that any undetected hypothyroidism will be mild enough so as to carry minimal risks to mother and baby. However, most ob/gyn or internal medicine practitioners who receive borderline lab results for pregnant women will refer the patient to an endocrinologist for further workup. This will certainly narrow the gap and reduce the instances of treatable disease going unnoticed, but any new symptoms during pregnancy should still always be reported to the treating physician immediately.
Questions for your doctor:
- What other conditions must be ruled out to make this diagnosis? (i.e., what is the differential diagnosis?)
- What lab tests do I need to have and when?
- Is there anything else I should be doing, not doing, or taking (besides thyroxine) to help avoid complications?
- How do you make the determination between normally reduced hormone levels of pregnancy and overt hypothyroidism?
- Are there any additional potential complications not mentioned in this article?
About the Author
Dr. Rothbard is a professional medical writer and consultant based in New York City, specializing in medical education articles targeted at a variety of audiences, from children through clinicians. After leaving medicine, he worked as a biology and medical science educator for several years, before deciding to pursue writing full-time. He may be reached at [email protected].