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(Date of issue: May 2016, Version: 1.1)

This is a UKTIS monograph for use by health care professionals. For case-specific advice please contact UKTIS on 0344 892 0909. To report an exposure please download and complete a pregnancy reporting form. Please encourage all women to complete an online reporting form.


Potassium iodide is an inorganic salt used in the management of iodine deficiency and thyroid disorders. Specific indications include systemic administration in conjunction with antithyroid drugs prior to partial thyroidectomy, in the treatment of thyrotoxic crises, as a thyroid protection agent following the release of radioactive-iodine and during MIBG scans. Potassium iodide is also used topically as an antiseptic for minor wounds, cuts and abrasions.

Iodine deficiency or excess can perturb normal fetal thyroid function and development. The World Health Organization recommends 250mcg/day iodine supplementation for pregnant and lactating women unless iodised salt is available.

Case reports document fetal goitre and abnormal fetal thyroid function, in some instances with persisting postnatal effects, following maternal potassium iodide treatment in pregnancy (at higher doses than used for supplementation). However, the degree to which the underlying maternal disease contributed to fetal outcome in some cases is uncertain. Limited evidence from a single study on pregnant women with Graves’ disease suggests that risk of spontaneous abortion and fetal congenital malformation may be reduced by switching from methimazole (a teratogen associated with a rare embryopathy) to potassium iodide early in the first trimester. A risk-benefit analysis that takes into account stage of pregnancy and likelihood of maternal disease relapse would, however, need to be undertaken on a case-by-case basis and routine switching is not currently advised. 

No association between in utero exposure to potassium iodide and the occurrence of low infant birth weight, preterm delivery, intrauterine death, neurodevelopmental delay or malignancy in the offspring has been identified. However, the extremely limited data render them unsuitable for use in a formal risk assessment, therefore increased risk cannot be ruled out.

Where potassium iodide is maternally administered at therapeutic doses, additional fetal and/or neonatal monitoring (e.g. fetal ultrasound, neonatal thyroid function tests) is advised as the presence of a fetal goitre or fetal thyroid dysfunction may impact on delivery and/or the postnatal wellbeing of the neonate. Early discussion with an obstetrician or materno/fetal medicine specialist is recommended for all women on potassium iodide therapy who are pregnant or planning a pregnancy.

Exposure to potassium iodide at any stage of pregnancy would not usually be regarded as medical grounds for termination of pregnancy. However, other risk factors may be present in individual cases which may independently increase the risk of adverse pregnancy outcome. Clinicians are reminded of the importance of consideration of such factors when performing case-specific risk assessments. Discussion with UKTIS is recommended in all cases of exposure.
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If you have a patient with exposure to a drug or chemical and require assistance in making a patient-specific risk assessment, please telephone UKTIS on 0344 892 0909 to discuss the case with a teratology specialist.

If you would like to report a pregnancy to UKTIS please click here to download our pregnancy reporting form. Please encourage all women to complete an online reporting form.

Disclaimer: Every effort has been made to ensure that this monograph was accurate and up-to-date at the time of writing, however it cannot cover every eventuality and the information providers cannot be held responsible for any adverse outcomes of the measures recommended. The final decision regarding which treatment is used for an individual patient remains the clinical responsibility of the prescriber. This material may be freely reproduced for education and not for profit purposes within the UK National Health Service, however no linking to this website or reproduction by or for commercial organisations is permitted without the express written permission of this service. This document is regularly reviewed and updated. Only use UKTIS monographs downloaded directly from or to ensure you are using the most up-to-date version.