Thyroid and pregnancy (targeted screening, treated hypothyroidism, Graves' disease)
BioMG follows French guidelines. Adapt it to the guidelines and the tests available where you practise.
Planning a pregnancy or early pregnancy: targeted screening
Laboratory tests (if risk factors)
- TSH
- Anti-TPO antibodies (if TSH > 2.5 mIU/L; not needed if already known to be positive)if neededTSH > 2.5 mIU/L in a pregnant woman or one planning pregnancy: anti-TPO antibodies assess the risk of progression to hypothyroidism during pregnancy and the risk of postpartum thyroiditis; a positive result is not repeated [1].
Do not order
Hypothyroidism treated with levothyroxine
Pregnancy plan
- TSH
As soon as pregnancy is established (after increasing levothyroxine by 20 to 30%), then every 4 to 6 weeks until 22 weeks of gestation
- TSH
Between 30 and 34 weeks of gestation
- TSH
6 weeks after delivery (return to the pre-pregnancy dose)
- TSH
Do not order
- Routine free T4 to follow treated hypothyroidism: NABM coverage limited (antithyroid drugs, clinical-biochemical discordance on levothyroxine) [7]
Graves' disease (current or past)
As soon as pregnancy is diagnosed
- TSH
- Free T4
- TSH receptor antibodies (TRAb)
Between 18 and 22 weeks of gestation (if TRAb high at the start)
- TSH receptor antibodies (TRAb)
- On antithyroid drugs: TSH and free T4 every 2 weeks after starting, then every 4 weeks once the target is reached (see the page Antithyroid drugs).
Postpartum thyroiditis (within the year after delivery)
Laboratory tests
- TSH
- Free T4 (if TSH abnormal)if neededAbnormal TSH: free T4 as a reflex test, on the same sample if the laboratory offers it [7].
- TSH receptor antibodies (TRAb) (thyrotoxicosis: thyroiditis or Graves' disease?)if neededPostpartum thyrotoxicosis: TRAb are the tool for the differential diagnosis of Graves' disease [2], whose risk of relapse is highest 7 to 9 months after delivery [2]. NABM indication: confirmation of Graves' disease outside the typical picture [7].
After the thyrotoxic phase: every 2 months until 1 year after delivery
- TSH
Sources (8)
- Haute Autorité de santé. Prise en charge des hypothyroïdies chez l’adulte (population générale, personnes âgées de plus de 65 ans, femmes enceintes). Recommandation de bonne pratique, validée le 15 décembre 2022 (mise en ligne mars 2023), chapitres 10 et 11.
- Kahaly GJ, Bartalena L, Hegedüs L, Leenhardt L, Poppe K, Pearce SH. 2018 European Thyroid Association Guideline for the Management of Graves' Hyperthyroidism. Eur Thyroid J. 2018;7(4):167-186.
- Alexander EK, Pearce EN, Brent GA, et al. 2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum. Thyroid. 2017;27(3):315-389.
- Nederlandse Vereniging voor Obstetrie en Gynaecologie (NVOG). Richtlijn Schildklierfunctiestoornissen, chapitre « Schildklierfunctiestoornissen voor, tijdens en na de zwangerschap » : dépistage et TRAb (11/04/2025), intervalle de référence de la TSH (13/05/2022), autres modules (2013, validité évaluée le 30/08/2021). Richtlijnendatabase.
- Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG). Subclinical hypothyroidism and hypothyroidism in pregnancy (C-Obs 46). Mars 2022.
- National Institute for Health and Care Excellence (NICE). Antenatal care. NICE guideline NG201, 19 août 2021.
- Assurance maladie. Nomenclature des actes de biologie médicale (NABM), version 105 : actes 1207 (T4 libre), 1208 (TSH), 1487 (anticorps anti-TPO), 1488 (anticorps antirécepteurs de la TSH) et 1211 (TSH + T4 libre, en cascade).
- Stagnaro-Green A, Abalovich M, Alexander E, Azizi F, Mestman J, Negro R, et al.; American Thyroid Association Taskforce on Thyroid Disease During Pregnancy and Postpartum. Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and postpartum. Thyroid. 2011;21(10):1081-1125.