Potassium Iodide During Pregnancy and Breastfeeding

Pregnant and breastfeeding women receive the full adult dose of potassium iodide (130mg) during a radiation emergency — but with a lower exposure threshold for initiating treatment and specific monitoring considerations.

Key Facts

• Dose: 130mg (same as adult dose)
• Exposure threshold: Lower than other adults (>5 cGy vs >10 cGy)
• Fetal thyroid begins concentrating iodine around 12 weeks gestation
• KI crosses the placenta — protecting the fetal thyroid but also suppressing it
• Single dose preferred when possible to minimize fetal thyroid suppression

Breastfeeding

Continue taking KI as directed, but the breastfed infant may also need their own separate dose based on their age category. KI is secreted in breast milk, but the amount may not provide complete infant protection. Consult health authorities for guidance.

Monitoring

After KI use during pregnancy, neonatal thyroid function should be monitored. Transient hypothyroidism is possible but typically resolves without treatment. However, unmonitored hypothyroidism in neonates can affect brain development.