If You Have Hashimoto’s, Should You Avoid Fish While You’re Pregnant?

If you have Hashimoto’s, should you avoid fish while you’re pregnant? During pregnancy, thyroid autoimmunity can worsen, or it can be initiated, because of the occilation of the immune system during pregnancy. Pregnancy is a high-risk time for thyroid autoimmunity. In this article we shed some light on the types of fish that are best during pregnancy.

During pregnancy, thyroid autoimmunity can worsen, or it can be initiated, because of the occilation of the immune system during pregnancy. Pregnancy is a high-risk time for thyroid autoimmunity.

During pregnancy, the titers of antibodies decrease to protect the fetus from abortion; but just after delivery, they increase again. The clinical implications are varied and concern the thyroid gland as well as other organs. Postpartum thyroid dysfunction (PPD) is one possible disturbance due to presence of antithyroid antibodies.

Serum positivity for thyroid autoantibodies is a predictive marker of postpartum thyroiditis and postpartum depression. Given this fact, the issue of fish consumption becomes a concern because fish contain mercury, and mercury may stimulate thyroid autoimmunity.

A recent study looked at this issue to evaluate the effects of consuming different types of fish during pregnancy.

Study Details

The researchers hypothesized that stable consumption of omega-3-rich oily fish was associated with a more favorable profile of serum thyroid antibodies throughout pregnancy and early postpartum compared with stable consumption of swordfish, a fish that concentrates pollutants like mercury.

The participants consisted of 236 thyroid disease-free, nonsmoker Caucasian women with stable dietary habits. The study measured serum thyroglobulin antibodies and thyroperoxidase antibodies in pregnancy (first and second trimesters) and postpartum (day 4).

The women were divided into four groups, consuming different types of fish—group A (swordfish), B (oily fish), C (swordfish plus other fish, not necessarily oily fish), and D (fish other than swordfish and oily fish).

The primary endpoints were positivity rates and serum concentrations of the two autoantibodies.

The positivity rates and serum concentrations of both antibodies were the greatest in group A and the lowest in group B, indicating that swordfish increases the rate of thyroid autoimmunity, but oily fish decreases the rate. Therefore, the more oily fish these women ate, the less thyroid autoimmunity they had. The oily fish included salmon, mackerel, sardines, trout, and herring.

The increase in thyroid autoimmunity when swordfish was consumed may be related to the mercury/selenium ratio. Certain fish may accumulate more mercury and have less selenium and may be more risky for thyroid autoimmunity.

The oily fish listed in this study are a safe bet because they will have less mercury and/or more selenium along with protective omega-3 fatty acids. Selenium helps to protect against and detoxify the mercury.

The estimated content of omega-3 fatty acids in the oily fish consumed by group B was the greatest. This suggests that the omega-3 fatty acids found in oily fish are very protective and beneficial during pregnancy.

If you have Hashimoto’s and you’re pregnant, we would not recommend avoiding oily fish because they can be very protective and helpful. Additionally, other studies have shown that the consumption of fish correlates to a higher IQ in the offspring.