[The immunologic situation of the placenta and its significance for disorders in early pregnancy].

Reference is made in numerous recent immunological studies to immunological mechanisms which were found to play a role in acceptance of pregnancy or habitual abortions. The most important theories likely to offer explanations for these phenomena are reviewed in some detail, including hormonal immunosuppression, immunologic-anatomic barrier at the placenta as well as blocking factors and anti-sperm antibodies. Molar pregnancy is associated with a particular immunological situation. None of the theories mentioned can be preferred, for the time being, to explain acceptance of normal pregnancy or the causes of recurrent spontaneous abortions.