Thyroid cancer and pregnancy

By (embryologist) and (fertility counselor).
Last Update: 02/16/2015

Thyroid cancer occurs due to a small number of malignant tumours, located in the thyroid gland. It is one of the most common endocrine cancers. Normally, malignant tumours originate in the follicular epithelium of the gland and are classified according to their histological features.

Undifferentiated tumours, such as anaplastic carcinoma, which tends to have a worse prognosis, don't usually respond to treatment and are very aggressive.

Diagnosis in pregnant women

In the body of a pregnant woman, many changes, which can mask the differentiated thyroid cancer, occur. However, several thyroid cancer signs can be detected: a nodule with a diameter bigger than 4 cm, presence of cervical lymphadenopathy, invasion of neck structures, distant metastases, history of irradiation during adolescence, a cold nodule that comes back and grows even after being aspirated and despite the treatment with levothyroxine.

The incidence of thyroid cancer is higher in women than in men. Recent studies point to external radiation as a major cause of thyroid cancer. The risk of cancer is not increased in patients who have been administered Iodine 131 during the treatment of other thyroid diseases.

Diagnostic tests

The diagnostic tests performed to detect the disease are:

  • High-resolution ultrasound: this test shows a poor node delineation, which usually has an irregular shape, the absence of a security halo, the calcification, the growth compared to previous scans and the Intranodal vascularization.
  • Fine needle aspiration (FNA). This test is fundamental for an early diagnosis of thyroid cancer. The biopsy of thyroid cells reveals papillary, medullary, follicular or anaplastic cancer. The test can be performed during pregnancy.
  • Thyroid scintigraphy. This test shows nodes that do not light up and is used on the whole body of the patient 3 days after thyroid cancer treatment. This test is only performed after pregnancy.


There are two main treatments:

  • Surgery: extraction or elimination of the cancer located in the thyroid. The surgeon will either perform a lobectom, that is to say, the extraction of the tissue where the cancer is located or a total thyroidectomy, that is, the removal of the entire thyroid gland. In some cases, lymph nodes can be removed to determine whether they had metastasized or not. The doctor, depending on the cancer type and stage of evolution, can decide to perform the surgery only after pregnancy.

Surgical tumour removal

  • Radioactive Iodine is a therapeutic option. It is used after surgery in patients diagnosed with thyroid cancer. The dose of this drug is much higher in the treatment of thyroid cancer. This treatment is not used for all types of thyroid cancer. When you're pregnant you cannot use radioactive iodine because it could damage or destroy the foetus' thyroid gland. After the treatment, the woman has to wait some time (indicated by the specialist) before getting pregnant.

Coping with pregnancy and cancer

It is difficult to cope with a cancer diagnosis during pregnancy. For this reason, experts recommend sharing your feelings with someone you trust, such as a family member, friend or counsellor. Many cancer centres have specialists who can help.

Before deciding, the patient and doctors must determine the best treatment and its possible risks to the foetus. The decision to undergo testing or treatment depends on the patient. Before making a decision the patient must be informed about the options, benefits and risks of the treatment. Depending on the status of the cancer and the pregnancy trimester, the physician may decide to wait until after childbirth to initiate the treatment.

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 Neus Ferrando Gilabert
Neus Ferrando Gilabert
B.Sc., M.Sc.
Bachelor's Degree in Biology from the University of Valencia (UV). Postgraduate Course in Biotechnology of Human Assisted Reproduction from the Miguel Hernández University of Elche (UMH). Experience managing Embryology and Andrology Labs at Centro Médico Manzanera (Logroño, Spain). More information about Neus Ferrando Gilabert
Adapted into english by:
 Sandra Fernández
Sandra Fernández
B.A., M.A.
Fertility Counselor
Bachelor of Arts in Translation and Interpreting (English, Spanish, Catalan, German) from the University of Valencia (UV) and Heriot-Watt University, Riccarton Campus (Edinburgh, UK). Postgraduate Course in Legal Translation from the University of Valencia. Specialist in Medical Translation, with several years of experience in the field of Assisted Reproduction. More information about Sandra Fernández

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