Monitoring Your Thyroid in Pregnancy: What You Need to Know

When you're pregnant (or planning to be), keeping an eye on your thyroid health is critical. Your thyroid hormones play a significant role in the healthy development of your baby, and ensuring your levels are within the right range can help you avoid potential complications during pregnancy. One of the most important hormones to monitor is TSH (Thyroid Stimulating Hormone).

In this post, we’ll discuss why it’s important to keep TSH levels in check, the ideal TSH levels for each stage of pregnancy, and how to support your thyroid health naturally.

Why Monitor Your TSH in Pregnancy?

Before pregnancy and throughout each trimester, the thyroid undergoes significant changes to meet your body’s increased needs. A TSH level that is too high can indicate an underactive thyroid, known as hypothyroidism, which can impact fertility, increase the risk of miscarriage, and affect your baby's growth and development.

But here’s the interesting part—TSH levels naturally decrease in early pregnancy due to the hormone HCG (human chorionic gonadotropin). HCG is produced by the placenta and is structurally similar to TSH, which means it can bind to the same receptors as TSH and stimulate the thyroid to produce more thyroid hormones. This extra stimulation causes TSH levels to drop during the first trimester.

While this drop in TSH is normal and expected in early pregnancy, it's still important to keep an eye on your levels to ensure they stay within the recommended range and don’t drop too low.

Pre-Pregnancy and First Trimester

Before you conceive, it’s important to ensure that your TSH levels are below 2.5. Studies have shown that TSH levels greater than 2.5 in the first trimester are linked to an increased risk of miscarriage. This makes it essential to keep your thyroid levels in check even before getting pregnant.

Once you’re pregnant, maintaining TSH levels below 2.5 remains critical throughout the first trimester. During this time, your body is working extra hard to support the early stages of your baby’s development, and the influence of HCG can cause your TSH to drop naturally.

When to test:

Pre-pregnancy
Between weeks 4-6 of pregnancy
Second and Third Trimesters

As you progress into the second and third trimesters, your TSH levels can naturally rise again as HCG levels decrease. However, it’s still recommended to keep your TSH under 3.0. Your thyroid continues to play a key role in your baby’s brain development, especially as they grow during the later stages of pregnancy.

When to test:
- Week 12
- Week 20
- Week 26
- Week 35
This testing schedule helps monitor any fluctuations in your TSH levels so we can respond quickly if necessary. In some cases, if I see a significant rise in TSH levels during pregnancy, I may recommend a small dose of thyroxine in collaboration with your doctor to help manage levels and support a healthy pregnancy.

Nutrients to Support Thyroid Health in Pregnancy

Beyond monitoring TSH levels, ensuring you’re getting the right nutrients to support thyroid hormone production is vital. I work closely with my clients to ensure they are getting enough of the following nutrients, which help keep the thyroid functioning optimally:
- Iron: Necessary for energy production and thyroid hormone synthesis.
- Selenium: Helps reduce thyroid inflammation and supports hormone conversion.
- Zinc: Supports overall hormone balance and thyroid function.
- Tyrosine: An amino acid that plays a critical role in thyroid hormone production.
- B Vitamins: Especially B6 and B12, these vitamins support energy and thyroid health.
- Iodine: Essential for thyroid hormone production, but must be handled carefully, especially for those with thyroid conditions like Hashimoto’s.
What About Hashimoto’s?

If you have Hashimoto’s thyroiditis, which is an autoimmune condition where the immune system attacks the thyroid, managing iodine levels becomes more complex.

Here’s what I do with my clients who have Hashimoto’s:
- Pre-Pregnancy & Early Pregnancy: I usually caution against iodine supplementation because it can sometimes aggravate the immune system, elevating TSH levels. I will usually test urinary iodine levels to assess need for iodine, and the prescribe at very low doses and monitor closely during pregnancy and post partum
- Second Trimester & Beyond: As pregnancy progresses, the immune system naturally suppresses, and I find that higher doses of iodine can be reintroduced without causing a spike in TSH or thyroid antibodies. This ensures that both the mother and the baby get the iodine they need for healthy thyroid function and development.
Your thyroid is a powerful driver of both your health and your baby’s development during pregnancy. By maintaining the right TSH levels and supporting your body with the right nutrients, you can ensure a smoother, healthier pregnancy journey.

If you’re thinking about getting pregnant or are already expecting, talk to your practitioner about monitoring your TSH levels throughout pregnancy, and don’t hesitate to reach out if you need support with thyroid health!

Want More Support with Your Thyroid Health?

I’ve helped countless women balance their thyroids naturally and safely through pregnancy. If you’re looking for personalised guidance or need more information on how to support your thyroid with the right nutrients, feel free to reach out to book a 1:1 session or check out my Thyroid Masterclass.