Iodine 131
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Iodine 131 is generally avoided in pregnancy as it can damage the baby’s thyroid gland and may affect the baby’s development.
What is iodine 131?
Iodine 131 is a radioactive form of iodine. Iodine in the body is naturally stored in the thyroid gland. Small doses of iodine 131 are used to picture the thyroid in medical scans. Iodine 131 is also used at higher doses to destroy excess thyroid tissue in the treatment of hyperthyroidism (overactive thyroid) and thyroid cancer.
Benefits
What are the benefits of using iodine 131 in pregnancy?
Use of iodine 131 in pregnancy is not recommended.
Risks
What are the risks of using iodine 131 in pregnancy?
Radiation from iodine 131 given in the first trimester could cause birth defects or a miscarriage. From 10-12 weeks of pregnancy, iodine 131 can damage the baby’s developing thyroid gland.
As iodine 131 can stay in the body for some time, it is recommended that women avoid getting pregnant for six months after exposure.
As a precaution, it is also recommended that pregnant women avoid prolonged contact with other people who have received iodine 131 within the past three weeks (such as sitting or sleeping next to them for several hours a day) to ensure that the baby is not exposed to too much radiation. Shorter-term contact with people who have received iodine 131 is not known to be unsafe for the baby.
Alternatives
Are there any alternatives to receiving iodine 131 during pregnancy?
Yes. If you are pregnant and need a thyroid scan or treatment for a thyroid condition, your doctor should be able to offer alternatives to iodine 131.
Will my baby need extra monitoring during pregnancy?
As part of their routine antenatal care, most women will be offered a scan at around 20 weeks of pregnancy to look for birth defects and to check the baby’s growth.
If you were exposed to iodine 131 during pregnancy, or you conceived within 6 months of treatment, you should tell your doctor or specialist as soon as possible. You may need additional scans to check the baby’s growth, development, and thyroid gland. Women with a history of thyroid cancer or other thyroid problems will be offered additional monitoring during pregnancy to ensure that their thyroid hormone levels stay at correct levels to support their own and their baby’s wellbeing.
Are there any risks to my baby if the father was treated with iodine 131?
Men who are treated with iodine 131 may wish to avoid conception for six months after treatment due to possible risks of radiation exposure on sperm development. However, small studies have not shown any ill effects on pregnancies fathered by men who received iodine 131 prior to conception. For more information on medicine exposure in fathers around the time of conception please see the bump leaflet on Paternal exposures.
Who can I talk to if I have questions?
If you have any questions regarding the information in this leaflet, please discuss them with your health care provider. They can access more detailed medical and scientific information from www.uktis.org.