[Incidence of postpartum thyroid function disorders in The Netherlands].

In a longitudinal study the incidence of postpartum thyroid dysfunction in the Netherlands was investigated in an unselected open population. There were 293 women who were screened by repeated assessments of thyroid function until 34 weeks postpartum at 6-week intervals. Thyroid dysfunction was defined as abnormal TSH values accompanied by abnormal FT4 and (or) FT3 values. The frequency of postpartum thyroid dysfunction was 7.2% (n = 21). Most of the thyroid dysfunction occurred between 16 and 28 weeks postpartum. There were five women with subclinical thyroid dysfunction: abnormal TSH values with complementary FT4 and (or) FT3 changes within normal limits. Four of them showed (marked) increase in antimicrosomal antibody titres. With the inclusion of the five women the frequency rose to 8.9%. These data appear representative for the Netherlands as a whole, suggesting that every year 14,000 women suffer from (transient) postpartum thyroid dysfunction.