Thyroid size and function in healthy pregnant women with thyroid autoantibodies. Relation to development of postpartum thyroiditis.

In a study of postpartum thyroiditis, thyroid function and ultrasonically determined thyroid size were evaluated in 36 thyroid autoantibody positive healthy women during pregnancy and the first postpartum year. Twelve women (33%) developed postpartum thyroiditis with permanent thyroid dysfunction in three. However, only one woman had symptoms and needed treatment. The most common type of thyroid dysfunction was a transient hyperthyroid phase as seen in 7 women. A significant increase by 20-30% in mean thyroid volume during pregnancy was demonstrated independent of development of postpartum thyroiditis. We conclude that initial thyroid volume or changes during pregnancy and post partum are not useful indicators of the development of postpartum thyroiditis. The fact that the condition is oligosymptomatic suggests that screening procedures are necessary if one wants to diagnose the earliest phases of postpartum thyroiditis.