A Guide on Thyroid During Pregnancy

Pregnancy is an exciting time, but it brings about unique hormonal changes in your body. The thyroid gland, a tiny butterfly-shaped gland in your neck, plays an essential role in your metabolism and your baby's development. However, the imbalances in its function can pose several challenges on your journey.

Thyroid issues in pregnancy are surprisingly common, with hyperthyroidism affecting 0.1–0.4% and hypothyroidism approximately 2-3% of pregnant women.

Understanding and managing these imbalances, whether an overactive (hyperthyroidism) or underactive (hypothyroidism) thyroid, is vital for protecting your health and your baby's.

In this guide, we'll discuss the complex link between your thyroid and pregnancy so you can address these hormonal changes and ensure a healthy pregnancy.

What is the Role of Thyroid Hormones in Pregnancy?

Your baby's brain and nervous system rely on thyroid hormones for proper development. In the first trimester (the first three months), your baby gets these essential hormones through the placenta. Around the 12th week, your baby's thyroid gland begins working independently, but it doesn't produce enough until 18-20 weeks - this triggers your normal thyroid functioning.

Pregnancy hormones like hCG (human chorionic gonadotropin) and estrogen can increase thyroid hormone levels in your blood, which makes diagnosing difficult. While the thyroid expands slightly in healthy pregnant women, it usually does not enlarge enough for a physical examination to detect it. Moreover, many symptoms of thyroid problems, like fatigue or weight changes, overlap with common pregnancy symptoms.

However, there are some symptoms easier to spot that may prompt your doctor to test you for hyperthyroidism or hypothyroidism.

What are the Symptoms of Thyroid in Pregnancy?

Symptoms of Hyperthyroidism in Pregnancy

Certain signs and symptoms of hyperthyroidism, such as an elevated heart rate, difficulty tolerating heat, and fatigue, usually occur in a healthy pregnancy. Additional signs of hyperthyroidism include:

• Rapid and irregular heartbeats
• Trembling hands
• Feeling too hot
• Trouble sleeping
• Frequent bowel movements or diarrhea
• A swelling in the front of the neck (goiter)
• Unexplained weight loss or a failure to gain the expected weight during pregnancy

Symptoms of Hypothyroidism in Pregnancy

Pregnant women with an underactive thyroid often share similar symptoms with individuals with hypothyroidism. Additionally, many pregnant women with hypothyroidism either have minimal symptoms or none. These signs and symptoms include:

• Extreme fatigue
• Difficulty tolerating cold temperatures
• Muscle cramps
• Severe constipation
• Challenges with memory or concentration
• Hoarse voice
• Swollen face
• Changes in the skin and hair, such as dry skin and eyebrow loss
• Carpal tunnel syndrome (hand tingling or pain)
• Irregular menstrual periods

READ: Changes to Expect in Your Body During Pregnancy

What Causes Thyroid in Pregnancy?

Pregnancy Causing Hyperthyroidism

Hyperthyroidism in pregnancy is typically caused by the same factors that lead to the condition in non-pregnant individuals. The most common cause (85-90%) is an autoimmune disorder known as Graves' disease. In individuals with Graves' disease, the immune system produces an antibody called thyroid-stimulating immunoglobulin (TSI). This antibody binds to thyroid cells and increases the production of thyroid hormones. \

Graves' disease is uncommon, affecting only 1 to 2 in 1,000 pregnancies.

Pregnancy Causing Hypothyroidism

Pregnancy-related hypothyroidism is typically caused by Hashimoto's disease, affecting 2 to 3 in 100 pregnancies. Hashimoto's disease is an autoimmune dysfunction where the immune system produces antibodies that target the thyroid. This causes inflammation and malfunction, which lowers the thyroid's ability to secrete the hormone.

How Does Thyroid Affect Pregnancy?

Now that you know the symptoms and causes of the condition, the next crucial question is - How does the thyroid affect pregnancy? Let's understand how hyperthyroidism and hypothyroidism can impact a woman's pregnancy.

Complications of Hyperthyroidism in Pregnancy

Pregnant women with hyperthyroidism don't usually experience complications. Mild hyperthyroidism typically doesn't cause issues for you or your unborn child, so your doctor may prescribe regular monitoring rather than treating the condition.

However, untreated and severe hyperthyroidism can lead to various complications, including:

• Miscarriage - loss of pregnancy
• Premature birth (early birth)
• Low birth weight
• Placental abruption
• Stillbirth - fetal death that occurs after 20 weeks of gestation.
• Preeclampsia – a dangerous increase in blood pressure during the final stages of pregnancy
• Maternal heart failure
• Thyroid storm – a sudden and severe escalation of symptoms
• Hyperemesis gravidarum – an extreme form of morning sickness characterized by excessive nausea and vomiting during pregnancy.

Complications of Hypothyroidism in Pregnancy

Severe and untreated hypothyroidism can cause multiple complications, such as:

• Anemia - a condition with low red blood cell count causing fatigue
• Preeclampsia
• Miscarriage
• Low birth weight
• Stillbirth
• Congestive heart failure (Rarely)

If you know you have hyperthyroidism or hypothyroidism, it's advisable to manage the condition before pregnancy to minimize risks. This involves undergoing two sets of thyroid tests (one month apart) to ensure your thyroid is functioning optimally and maintaining a consistent level of hormones.

During pregnancy, regular monitoring and following prescribed medication can help prevent potential complications.

How to Reduce Thyroid During Pregnancy?

Options for Treating Hyperthyroidism During Pregnancy

Most doctors give antithyroid medications like propylthiouracil and methimazole to pregnant women to effectively manage hyperthyroidism. They help control thyroid hormone levels and improve symptoms. Propylthiouracil (PTU) is preferred in the first trimester, while methimazole (MMI) may be used later in pregnancy.

Hyperthyroidism triggered by hyperemesis gravidarum may not require medication for the thyroid itself. Treatment for dehydration and vomiting is often sufficient.

While uncommon, surgery to remove part of the thyroid gland might be necessary for individuals with medication allergies or severe goiters. However, doctors generally avoid surgery during pregnancy due to potential risks.

Options for Treating Hypothyroidism During Pregnancy

Treating hypothyroidism during pregnancy requires replacing the missing hormones that the thyroid doesn’t produce anymore. Typically, your doctor will prescribe levothyroxine, a thyroid hormone medication that works like T4, one of the hormones naturally produced by the thyroid. Levothyroxine is safe for both you and your baby and is especially important for supporting your baby's growth until they can make their thyroid hormones.

FAQs

1. What Should be the Thyroid Level to Get Pregnant?

Optimal thyroid levels for pregnancy vary, but TSH (thyroid-stimulating hormone) levels of 2.5 mIU/L or below are generally recommended when trying to conceive and 3.0 mIU/L during pregnancy. Maintaining these levels is crucial for fertility and a healthy pregnancy.

2. How to Treat High TSH in Pregnancy?

High TSH indicates that your thyroid is not making enough thyroid hormone (hypothyroidism). Treating high TSH in pregnancy involves thyroid hormone replacement therapy, typically with levothyroxine - a medication that works like the T4 hormone produced by the thyroid. Regular monitoring and proper dosage adjustments are crucial to maintain TSH levels within the recommended range (0.1-2.5 mIU/L in the first trimester, 0.2-3.0 mIU/L in the second, and 0.3-3.0 mIU/L in the third).

3. When to Check Thyroid Levels After Pregnancy?

You can check your thyroid level every eight weeks for the first nine postpartum months.

Take Away

Thyroid during pregnancy is common among women, and understanding and managing these thyroid issues during pregnancy is crucial for maternal and fetal health. Regular monitoring, early detection of symptoms, and appropriate medical treatment can help mitigate potential complications.

Remember to consult your doctor to ensure a smoother pregnancy journey and promote your and your baby's well-being.