Background: Depression and thyroid dysfunction are prevalent in women, including pregnant women. The aim of this study was to assess the relationship between depression and thyroid function during pregnancy.
Methods: One hundred and ninety-nine pregnant women three times during pregnancy were assessed for depressive disorder and for thyroid stimulating hormone (TSH) and free thyroxine (FT(4)) concentrations.
Results: Prevalence of depressive disorder was 6.5% in early pregnancy, 3.0% in middle pregnancy and 3.5% in late pregnancy. There were no women with overt thyroid dysfunction. Subclinical hyperthyroidism was found in 23% of women in early pregnancy, in 5% of women in middle pregnancy and in 6% of women in late of pregnancy. In late pregnancy depressed women compared to non-depressed women had significantly higher FT(4) concentrations and a strong trend towards lower TSH concentrations as well as higher prevalence of subclinical hyperthyroidism.
Conclusions: These findings show an association between thyroid dysfunction and depression in late pregnancy. Because gestational depression might interfere with pregnancy outcome, evaluation of thyroid function during gestation is warranted.