2025-05-09 | Category: Mrcog 2

🆕 GTG No. 76: Management of Thyroid Disorders in Pregnancy (2025)

RCOG Green-top Guideline No. 76 | First Edition | April 2025

📘 Scope & Purpose

This is the first edition of GTG No. 76, which replaces outdated fragmented guidance on thyroid disorders during pregnancy. It provides evidence-based and consensus-driven recommendations for diagnosing, monitoring, and treating thyroid dysfunction in pregnancy. It focuses on pregnant individuals, excluding those seeking conception or with recurrent miscarriage (covered under RCOG SIP No. 65).

🔑 Key Recommendations

🧪 Thyroid Function Tests (TFTs)

• Use trimester- and assay-specific reference ranges for TSH and fT4.
• If unavailable, use TSH upper threshold of 4.0 mU/L in pregnancy (Grade C).
• Use treatment targets, not diagnostic thresholds, for patients on LT4 or antithyroid drugs.

🧂 Iodine Supplementation

• Recommend total intake of 200–250 μg/day during pregnancy and lactation.
• Routine 150 μg/day potassium iodide supplementation is advised preconception and during pregnancy.
• Avoid iodine intake > 500 μg/day (risk of thyroid dysfunction).

🧫 Screening Approach

• Universal TFT screening is not recommended (Grade C).
• Targeted testing is advised in:
• History of thyroid disease or surgery
• Autoimmune disorders (e.g., SLE, T1DM)
• Previous stillbirth or 2nd trimester miscarriage

🩺 Hypothyroidism

• Pre-pregnancy TSH goal: ≤2.5 mU/L
• On positive pregnancy test, increase LT4 dose by 25–30%
• e.g., double the dose on 2 days/week
• Monitor TFTs:
• Every 4–6 weeks until 20 weeks
• Again at 28 weeks
• Subclinical Hypothyroidism  (TSH >10 mU/L): Treat with LT4
• SCH with TSH 4–10 mU/L: Consider LT4 if TPOAb+ or early pregnancy
• IH (normal TSH, low fT4): Routine treatment not recommended

💊 Hyperthyroidism

• PTU preferred in first trimester; switch from CMZ before 10 weeks
• Stable Graves’: Consider stopping ATDs if euthyroid ≥6 months
• Monitor TFTs every 2–4 weeks until 20 weeks, then 4–8 weeks

🧬 TPO Antibodies

• Do not routinely test for TPOAb in euthyroid women.
• No LT4 treatment for TPOAb+ women without thyroid dysfunction.
• If TPOAb+ and euthyroid: Monitor TFTs at booking and at 20 weeks.

👶 Postpartum Management

• Revert to pre-pregnancy LT4 dose at 2 weeks postpartum.
• Stop LT4 in women newly started during pregnancy; test TFTs at 6 weeks postpartum.

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