We report a preterm breastfed infant who developed a transient hypothyroidism after his lactating mother had a CT scan with iodinated contrast medium, despite the advised 24 hours’ pause in breast feeding. The aetiological assessment did not show any other cause for this hypothyroidism. Transient neonatal hypothyroidism after the use of topical iodine is well known, but it has not been described as a complication of intravenous contrast medium administration to a lactating mother. This case highlights the possibility of transient neonatal hypothyroidism secondary to contrast medium exposure to a lactating mother. When imaging is needed in the lactating mother, a longer break in breast feeding might be needed to prevent transient hypothyroidism in the preterm infant.

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