The American Thyroid Association has released its 2026 guideline for managing thyroid disease in women who are planning to conceive, pregnant, or postpartum, updating its 2017 recommendations. This full guide covers various aspects of thyroid health, including testing, iodine intake, infertility, hypothyroidism, thyroid autoimmunity, and postpartum care. A multidisciplinary team of experts, comprising thyroid specialists, obstetricians, reproductive medicine specialists, a methodologist, and a patient representative, collaborated to develop the guideline. Their recommendations were informed by feedback from stakeholders, a global needs assessment of 388 respondents, and 122 PICO questions.
Systematic reviews of literature were conducted with the help of a medical librarian, and the recommendations were graded using the GRADE framework, considering factors such as evidence certainty, benefits, and harms. In cases where direct evidence was limited, Good Practice Statements were used to establish a clear standard of care. The guideline emphasizes that while the recommendations represent the current best practice, the supporting evidence is often of low to moderate quality, highlighting the need for individualized care through clinical judgment and shared decision-making.
Changes in Levothyroxine Treatment Approach
A significant shift in the guideline is the move away from treating patients with normal thyroid function who test positive for thyroid peroxidase antibodies (TPOAb) solely based on their antibody status. According to the guideline, levothyroxine should not be prescribed to women with normal thyroid function who are TPOAb-positive and experiencing infertility or recurrent pregnancy loss, as three high-quality randomized trials found no improvement in fertility or pregnancy outcomes. Instead, these women should undergo regular thyroid function monitoring every 3 to 6 months while trying to conceive. Similarly, TPOAb status is no longer a determining factor for treating subclinical hypothyroidism during pregnancy, with treatment decisions now focusing on the severity and persistence of biochemical dysfunction and the stage of pregnancy.
Importance of Confirming Mild Thyroid Abnormalities
The guideline recommends that patients with mild elevations in thyroid-stimulating hormone (TSH) levels, particularly those below 6 mU/L, should undergo repeat thyroid testing before starting levothyroxine treatment. This is because many mild thyroid abnormalities can resolve on their own within a few weeks, and delaying treatment has not been shown to cause harm. Additionally, treatment initiated after the first trimester has not been proven to improve pregnancy or childhood neurocognitive outcomes in cases of subclinical hypothyroidism.
Targeted Screening and Postpartum Care Strategies
The guideline now advises a targeted approach to thyroid screening, where clinicians evaluate each newly pregnant patient for thyroid disease risk factors and offer TSH testing to those at increased risk. Maternal age, BMI, parity, and a history of miscarriage are no longer considered sufficient indications for testing on their own, as evidence is still lacking to support universal screening before, during, or after pregnancy. Laboratory- and trimester-specific reference intervals for TSH and free T4 are preferred, and when unavailable, a TSH interval of approximately 0.1 to 4.0 mU/L can be used during the first and second trimesters. TSH remains the most reliable marker of maternal thyroid status, and the same assay should be used throughout follow-up when possible.
Clinicians should exercise caution when prescribing levothyroxine therapy, reserving it for cases where clinical urgency or a high likelihood of persistent disease warrants immediate treatment. For patients with normal thyroid function who are TPOAb-positive or thyroglobulin antibody-positive and experiencing infertility or recurrent miscarriage, levothyroxine has not been shown to improve conception, miscarriage, or live-birth outcomes. Regular monitoring of thyroid function using TSH is recommended, as some patients may develop hypothyroidism before or during pregnancy.
Postpartum follow-up and counseling should be integrated into prenatal care, with patients at increased risk being informed about the potential for thyrotoxic and hypothyroid phases of postpartum thyroiditis. Patients with a history of postpartum thyroiditis should undergo thyroid testing at 1 year or sooner if symptoms develop and receive counseling on recurrence and symptoms that warrant testing.
Clinical Recommendations and Guidelines
Pregnant and lactating women should aim for a daily iodine intake of 250 mcg, as recommended by the guideline. However, urinary iodine concentration is not a reliable indicator of chronic iodine deficiency in individuals, and clinicians should consider dietary patterns, geographic risk, malabsorption, use of iodized salt, and supplement intake instead. Iodine intake above 500 mcg daily should be avoided due to the risk of maternal and fetal thyroid dysfunction. For isolated hypothyroxinemia, initiating levothyroxine treatment during the second trimester has not been proven to improve obstetric or childhood neurocognitive outcomes, and the guideline does not recommend it.
Repeat testing in 2 to 6 weeks may be considered when hypothyroxinemia is detected early in pregnancy, along with assessment for iron or iodine deficiency. Urgent thyroid surgery should not be delayed solely due to pregnancy and can be performed during any trimester when clinically required, although the second trimester is generally preferred when timing is flexible. Most low-risk differentiated thyroid cancers can be managed according to principles used outside pregnancy, and treatment can often be deferred until postpartum, while higher-risk disease should be managed according to oncologic indications similar to those in nonpregnant patients.
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