Pregnancy & thyroid cancer

Before diving into this month’s topic, we would like discuss the leaked document from the United States Supreme Court on overturning Roe v. Wade— a decades long precedent ensuring a woman’s right to safe abortions— and the consequences for a young woman facing a cancer diagnosis. In most cases those diagnosed with Papillary and Follicular Thyroid Cancer are able to carry to full term prior to undergoing treatment. There is insufficient research when it comes to Anaplastic and Medullary Thyroid Cancer when radiation, external beam radiation and chemotheraphy are forms of treatment.

ThyTabono stands with Young Women in the AYA Cancer Community and urges Justices and elected lawmakers to consider the harmful ramifications that ending constitutional protections for abortion could have on women facing a cancer diagnosis – further magnifying the feeling of fear, anxiety and trauma.

Finding out about a thyroid cancer diagnosis during pregnancy

Did you know? Thyroid cancer is the second most commonly diagnosed malignacy in pregnancy

If you are pregnant when diagnosed with thyroid cancer, your doctor will have specific instructions related to your pregnancy. A woman who is pregnant or breastfeeding should never receive RAI in any form (I-123 or I-131). Also, pregnant women should not be treated with external beam radiation or chemotherapy until after the baby is born.

In pregnancy, thyroid tumors very often do not progress, and pregnant women have successfully waited to postpone surgery until after pregnancy. If surgery is necessary sooner, it is usually performed in the second trimester (22 weeks of pregnancy).

Trying to conceive after thyroid cancer

Is it risky? Is there an increased risk of recurrence?

Pregnancy does not cause thyroid cancer recurrence in PTC survivors who have no structural or biochemical evidence of disease persistence at the time of conception. However, in the presence of such evidence, disease progression may occur during pregnancy, yet not necessarily as a consequence of pregnancy.

An undiagnosed or uncontrolled thyroid disorder can make it harder to conceive and can cause problems during pregnancy.

If you have an untreated (or undertreated) underactive thyroid gland (hypothyroidism), you may find it more difficult to conceive. Women may have longer or heavier periods, which can cause anemia, or your periods may stop completely. Men’s fertility may also be affected and they may be less likely to father a child if their thyroid hormone levels are low. However, once you are taking medication (levothyroxine tablets) and your thyroid hormone levels are back to normal your chances of becoming pregnant, or fathering a child, should improve dramatically.

Post-radioactive iodine (RAI) treatment

In women, radioactive iodine therapy has been associated with irregular menstrual cycles, earlier menopause, and delayed pregnancy. Women who receive radioactive iodine therapy are generally advised to avoid pregnancy in the 6-12 months after treatment, due to the risks of radiation to the eggs within the ovaries.

The importance of monitoring

“Pregnancy after thyroid cancer is doable and is very closely monitored to help keep the pregnancy safe… I had an incredibly traumatic, scary birth giving to 2 two pound, very ill babies that spend 62 days in the NICU.”

-Brie, thyroid cancer survivor

For the first 18-20 weeks of pregnancy, the baby is completely dependent on the mother for the production of thyroid hormone.

By mid-pregnancy, the baby’s thyroid begins to produce thyroid hormone on its own. The baby, however, remains dependent on the mother for ingestion of adequate amounts of iodine, which is essential to make the thyroid hormones. Levothyroxine requirements increase as early as the fifth week of gestation. It’s important to check levels and work with your endocrinologist as soon as pregnancy is confirmed and throughout the pregnancy to ensure the correct dosage of hormone replacement

Hypo- vs. hyper-thyroidism

Ideally, hypothyroid women should have their levothyroxine dose optimized prior to becoming pregnant. Levothyroxine requirements frequently increase during pregnancy, usually by 25 to 50 percent. Thyroid function tests should be checked approximately every 4 weeks during the first half of pregnancy to ensure that the woman has normal thyroid function throughout pregnancy. As soon as delivery of the child occurs, the woman may go back to her usual pre-pregnancy dose of levothyroxine.

“I did find a community of fellow thyroid cancer survivors, including a few who shared their stories of getting pregnant and having kids of their own after treatment. It gave me hope. ”

-Berna, ThyTabono Board Member


Breastfeeding is safe while taking levothyroxine.

Some breastfeeding mothers with hypothyroidism struggle to make a full milk supply. Thyroid hormones play a role in normal breast development and helping breasts to make milk. When not enough of the thyroid hormones are made, a mother’s milk supply may be affected. Women who have been treated with controlled hormone levels report they have no problems with supply.

Talk to lactation consultant/endo before taking supplements.

Some supplements that are commonly used to increase milk supply can interact with thyroid medication or function. Mothers with thyroid issues should be cautious in using fenugreek as a lactation aid. Fenugreek is one of the most popular supplements used to increase milk supply, and while some studies show promising results, women taking thyroid medication should avoid it or carefully monitor their thyroid levels if they choose to use it.

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