Goitre in Pregnancy

Goitre in pregnancy is enlargement of the thyroid gland, either diffuse or nodular. Causes are iodine deficiency, autoimmune thyroiditis, Graves disease, multinodular goitre and hCG stimulation. Mild enlargement of 10 to 15 percent is normal in pregnancy, but visible goitre needs assessment. Iodine deficiency remains common in some regions and matters because it causes maternal hypothyroidism and fetal brain damage.

• Risk factors: iodine deficient areas, family history, smoking, autoimmune disease.
• Daily iodine need in pregnancy is 250 micrograms.
• Thyroid function must be checked in every goitre.

Women have a visible neck swelling, tightness, difficulty swallowing or breathing, hoarseness and sometimes features of hypo or hyperthyroidism. Examine size, consistency, nodules, bruit, retrosternal extension and nodes.

• Pemberton sign for retrosternal goitre.
• Diffuse smooth goitre is common in iodine deficiency.
• Differential diagnosis: physiological enlargement, iodine deficiency goitre, Hashimoto thyroiditis, Graves disease, multinodular goitre, thyroid nodule or cancer, thyroiditis.
• Complications: airway compression, hypothyroidism, hyperthyroidism, miscarriage, preeclampsia, fetal goitre, cretinism from severe deficiency.

The approach is clinical with thyroid function tests and ultrasound.

• TSH and free T4; thyroid peroxidase antibodies; TSH receptor antibodies if hyperthyroid.
• Neck ultrasound: gland volume, nodules, calcifications.
• Urinary iodine where available: median below 150 micrograms/L in pregnancy suggests deficiency.
• Flow volume loop or chest X-ray with shielding for retrosternal extension if breathing symptoms.

The principle is to treat the underlying cause, give iodine and avoid radioactive iodine.

• Supportive: iodised salt in food; iodine rich foods such as fish and dairy; stop smoking; teach to report breathing difficulty.
• Pharmacological: potassium iodide 150 micrograms oral daily (total intake 250 micrograms with food) for iodine deficiency; avoid doses above 500 micrograms daily; levothyroxine 1.6 to 2.0 micrograms/kg oral daily for hypothyroidism to keep TSH at 0.1 to 2.5 mIU/L in the first trimester and below 3.0 mIU/L later; for Graves disease give propylthiouracil 100 mg oral 8-hourly up to 16 weeks and then carbimazole 10 to 20 mg oral daily; folic acid 400 micrograms oral daily to 12 weeks.
• Procedures: thyroidectomy in the second trimester for airway compression or suspected cancer.
• Special groups: women with a retrosternal goitre and airway narrowing need anaesthetic assessment before delivery; neonates have heel prick TSH at 3 to 5 days.
• Red flags: stridor, breathing difficulty, rapid growth, hoarseness, hard fixed lump, neck nodes.
• Follow-up: TSH every 4 weeks if on treatment; ultrasound at 4 to 8 weeks for growth; thyroid function at 6 weeks postpartum.