[Thyroid changes in the pregnant woman]

In Belgium the iodine intake is restricted and even marginally insufficient. During pregnancy, the insufficient iodine supply is associated with chronic stimulation of the thyroid gland, leading to the development of gestational goiters and to an increased risk of foetal goitrogenicity. Also, approximately one third of pregnant women exhibit relative hypothyroxinemia. Moreover, women who present chronic autoimmune thyroiditis and in whom thyroid function is normal at the onset of pregnancy carry a significant risk of developing thyroid insufficiency during gestation. In conclusion, healthy pregnant women should be given the benefit of iodine supplementation, both during pregnancy and breastfeeding. This will allow them to maintain a well adapted thyroid function, prevent goitrogenicity, and ensure adequate foetal hormone production. For women with autoimmune thyroiditis, thyroid function should be closely monitored during pregnancy and the slightest indication of thyroid insufficiency should prompt the administration of thyroid hormone substitution.