Section for epidemiology and medical statistics

Pregnancy and risk of thyroid cancer in the mother

A Nordic study that was recently published in the American Journal of Epidemiology shows that conditions related to pregnancy are important for the later development of thyroid cancer in the mother.

Thyroid cancer

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The incidence of thyroid cancer is higher among women than among men, especially in women of reproductive age. The only known modifiable risk factors for the disease are radiation and obesity. Few studies have previously looked at the importance of conditions linked to pregnancy and the subsequent development of thyroid cancer in the mother.

We conducted a large case-control study where we combined data from the birth and cancer registers in Denmark, Finland, Norway and Sweden in the period 1967 to 2015. The study included over 7,400 women with thyroid cancer aged 18 to 86 and approx. 67,900 women without cancer.

The results showed that conditions related to pregnancy, especially high parity (number of children), high age at first pregnancy, severe pregnancy sickness, bleeding after birth, diseases of the thyroid gland (hypothyroidism, hyperthyroidism, goiter and benign tumors), and high birth weight of the child were associated with an increased later cancer risk in the mother. Several of these factors were also associated with an increased risk of advanced disease.

Maternal health, pregnancy and offspring factors, and maternal thyroid cancer risk: a Nordic population-based registry study