How to manage a thyroid nodule during pregnancy?

Management of Thyroid Nodules During Pregnancy

All thyroid nodules discovered during pregnancy should be evaluated with fine-needle aspiration biopsy (FNA), as up to 40% may be malignant, and management decisions depend critically on cytology results and gestational timing. 1

Initial Evaluation Approach

Perform ultrasound-guided fine-needle aspiration biopsy for all thyroid nodules, particularly those >1 cm or with suspicious ultrasound features. 2, 3, 4

• FNA has excellent diagnostic accuracy during pregnancy, with 100% concordance between benign cytology and histology 2
• Cytology showing papillary cancer has 100% concordance with final histology 2
• Radioactive iodine scanning is absolutely contraindicated during pregnancy 1, 3
• Ultrasound assessment should evaluate nodule size, characteristics, and any concerning features 4

Management Based on Cytology Results

Benign Cytology

• Monitor conservatively with serial ultrasounds 2, 4
• Thyroid nodules may increase in size during pregnancy (mean diameter increase of 0.7 mm by third trimester), but this growth is typically not clinically significant 5
• Thyroid volume increases during pregnancy and remains elevated 3 months postpartum 5
• Surgery can be safely deferred until the postpartum period 2

Malignant or Suspicious for Papillary Cancer

• Perform thyroidectomy during the second trimester if nodule is discovered early in pregnancy 1, 2, 6
• Surgery in the second trimester carries lower risk than first or third trimester 1
• Start levothyroxine immediately after diagnosis to suppress TSH 6
• Most thyroid cancers detected during pregnancy will not grow significantly or pose immediate risk during gestation 4

Suspicious for Follicular Neoplasm

• Defer surgery until the postpartum period 2
• Only 0% of follicular neoplasm cytology proved malignant in pregnancy studies (all were benign adenomas) 2
• Start TSH-suppressive levothyroxine therapy during pregnancy 6

Timing Considerations

For nodules discovered late in pregnancy (third trimester), defer complete workup until after delivery. 6

• Early pregnancy discovery (first/early second trimester): Proceed with FNA immediately and plan surgery if malignant 2, 6
• Late pregnancy discovery: Monitor with ultrasound, defer FNA and definitive treatment until postpartum 6
• Serum thyroglobulin can be used as a noninvasive marker to evaluate disease status during pregnancy 6

Critical Safety Points

• Radiation therapy (I-131) must not be administered until after pregnancy is completed 1
• Women should not breastfeed for 4 months after I-131 treatment 1, 7, 8
• Thyroidectomy can be performed safely under local or general anesthesia during pregnancy when indicated 6
• Coordinate care between endocrinology, surgery, and maternal-fetal medicine 3

Postpartum Management

• Complete any deferred evaluations (FNA, surgery) in the early postpartum period 2
• For confirmed malignancy requiring radioactive iodine, delay treatment until after breastfeeding is discontinued 1
• Continue TSH-suppressive levothyroxine therapy for diagnosed thyroid cancer 6