Hashimoto’s Thyroiditis: Thyroid Effects During Pregnancy

Feeling colder than everyone else? Noticing hair loss and weight gain? Are you more tired, moody, and achy than usual? Hashimoto’s thyroiditis is an autoimmune condition that causes the thyroid to produce too little hormone. Left untreated, hypothyroidism can cause serious problems for both mother and baby during pregnancy.

Key takeaways:

If you are experiencing symptoms, it is important to discuss your thyroid levels with your doctor so that you can optimize care prior to conception and throughout pregnancy.

What is Hashimoto’s disease?

Hashimoto’s disease is an autoimmune condition that affects the thyroid and tends to have a hereditary link. The thyroid gland sits at the base of your neck and secretes hormones that are important for many bodily functions, including heart rate, body temperature, and metabolism. People who develop Hashimoto’s disease have antibodies that attack their thyroid gland. In about 20-30% of people, this causes it to produce too little hormone, which can lead to poor outcomes for the mother and baby.

According to Vibhavasu Sharma, MD, FACE of the Albany Medical College in Albany, New York, “Thyroid disease is commonly encountered during pregnancy.” Writing for the American Thyroid Association, Dr. Sharma reassures pregnant women that, “Our current scientific understanding can provide some practical guidance to optimize care.”

Hashimoto’s disease effect on pregnancy

The baby is completely dependent on the mother’s production of thyroid hormones for the first 18-20 weeks of gestation. From midway through the second trimester, the baby’s thyroid can start producing the hormone but it's still dependent on the mother for adequate iodine. This is why a supplement with at least 150 mcg of iodine is recommended during pregnancy.

If hypothyroidism develops during pregnancy but is untreated, it can lead to health problems for the mother including:

  • Preeclampsia. High blood pressure, high levels of protein in the urine indicating kidney damage or other organ damage.
  • Anemia. Low levels of iron in the blood.
  • Miscarriage. The loss of the baby pre-term.
  • Placental abruption. Partial or complete separation of the placenta from the uterine walls.
  • Postpartum bleeding. Excessive loss of blood post delivery.

The baby can also suffer serious problems such as birth defects like cleft palate, developmental problems, premature birth, low birth weight and stillbirth.

Hashimoto’s disease symptoms

The thyroid secretes hormones that affect every cell in the body, therefore symptoms can be diverse and may not be apparent initially. Some women might even have overactive thyroid symptoms at first, such as increased resting heart rate, palpitations, and sleeplessness.

As the disease progresses, other symptoms to watch for include the following:

  • Cold intolerance. You'll notice yourself being more sensitive to the cold.
  • Mood swings. You may be more prone to intense shifts in your emotional state.
  • Hair and nail changes. It's common to notice more brittle hair and nails.
  • Joint pain. You may notice pain in your joints.
  • Dry skin. Skin often becomes dry and flaky.
  • Brain fog. You might find it difficult to concentrate on tasks you usually find easy.
  • Constipation. Going to the toilet might become more strained.
  • Heavier menstrual periods. Some people notice an increase in the amount of menstrual blood.
  • Weight gain. It's common to put on weight with this disease.
  • Enlarged thyroid (goiter). You might notice a larger lump at the front of your neck which may make swallowing more difficult.

Causes of Hashimoto’s disease

The autoimmune condition is thought to be caused by genetic predisposition and environmental factors. If the body loses immune tolerance for the thyroid gland, immune cells begin to attack the thyroid. Sometimes thyroiditis (inflammation of the thyroid) can happen following pregnancy, but it usually resolves within 12-18 months.

Risk of developing Hashimoto’s disease

Certain groups and those affected by different health conditions are more at risk of developing Hasimoto's thyroiditis.

  1. Gender. The condition typically affects more women than men.
  2. Age. You are more at risk between the ages of 40 and 60 years.
  3. Genetics. You are more at risk if you have a family history of autoimmune conditions such as celiac disease.
  4. Pre-existing health conditions. Risk factors include type 1 diabetes, rheumatoid arthritis and lupus.

How is Hashimoto’s diagnosed

To diagnose Hashimoto’s disease, your primary care doctor will take a medical history, discuss your symptoms, and do a physical exam. One or more blood tests will be done to check for hypothyroidism.

Blood tests to diagnose Hashimoto’s disease include thyroid hormones T3 (triiodothyronine) and T4 (thyroxine), thyroid stimulating hormone (TSH), and thyroid peroxidase antibodies (TPO).

Your doctor may also recommend an ultrasound if you do not have any anti-thyroid antibodies in your blood. This will allow the doctor a chance to look for nodules (bumps) on the thyroid which may be causing enlargement.

Can Hashimoto’s be treated during pregnancy?

Yes, careful management of Hashimoto’s during pregnancy can help reduce the risk of poor outcomes for both mother and baby.

  • Drug therapy. Levothyroxine is bioidentical to T4 and can be used to treat pre-existing or newly diagnosed hypothyroidism during pregnancy. Triiodothyronine (T3) is not currently recommended during pregnancy because it may impede transfer of maternal T4 to the fetal brain.
  • Pre-conception counseling. Women with pre-existing hypothyroidism should have a preconception counseling visit to talk about how to manage the condition through pregnancy, such as how often to test, what medications to take, and how to manage the dosage during each trimester.
  • Hormone replacement. Women with elevated Hashimoto’s antibodies (TPO) and subclinical hypothyroidism (TSH >4mU/L with normal T4) may benefit from hormone replacement with levothyroxine to prevent miscarriage. Women without elevated TPO may be considered for hormone replacement at a higher TSH level (such as 10 mU/L). This would be an important conversation to have with your doctor or endocrinologist.

Importance of preconception planning

Approximately 50% of women who have Hashimoto’s may have had trouble conceiving. This may be an early warning sign that thyroid function should be checked. A preconception medical appointment is recommended by the CDC to review any health conditions which need to be managed, check on needed vaccines, and discuss medications that might need to be started or paused during pregnancy.

Men also benefit from a preconception wellness visit to get in the best possible health before welcoming a child. While we may not think of this often, lifestyle choices do affect sperm quality, meaning the father has a chance to impact the future health of his child by improving his health.

The key message for women is to talk to their doctor regularly. If you are planning on conceiving, ask your doctor about your thyroid function so that you can start treatment right away if needed. If you have already delivered, you may be experiencing post-partum thyroid abnormalities which are worth discussing with your doctor as well. Remember, these often resolve within a year or so.


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