Autoimmune thyroiditis has important consequences for fertility, the occurrence of pregnancy complications, pregnancy outcome. Moreover autoimmune thyroiditis can aggravate during the postpartum period. Finally, the sequelae of autoimmune thyroiditis might have important consequences for the offspring. Several studies have shown an association between thyroid autoimmunity in earlyas opposed to beforepregnancy and subsequent "incidental" miscarriage. With respect to habitual abortion available data are more conflicting perhaps mild degrees of thyroid insufficiency - not detectable by routine thyroid testing - and not thyroid autoimmunity per se is causal in the association between the presence of thyroid antibodies and recurrent abortion. Autoimmune hypo- and hyperfunction during pregnancy are both related to obstetrical complications. It is important to note that treatment can - at least in part - reduce this excess risk associated with untreated hypo- or hyperthyroidism. Considering pregnancy outcome there are now data providing evidence that not only overt but also relatively mild and hitherto unrecognized states of thyroid failure are associated with persistent and significant impairment in neuropsychological performance of the offspring. Postpartum thyroiditis is clearly associated with the presence of TPO antibodies (i.e. autoimmune thyroiditis). Autoimmune thyroiditis is thus clearly associated with clinically relevant events, occurring before, during and after pregnancy. Screening should be considered; however further research is urgently needed.