The natural course of habitual abortion.

In recurrent spontaneous abortion an immunological fetal-maternal imbalance has been postulated and successes of immunotherapy have been described. A prospective study on the reproductive performance of untreated women with three abortions of unknown etiology has not been performed. The benefit of therapy can only be estimated if the natural course of the disease is known. The aim of this study was to investigate prospectively the abortion rate in a well-defined group of women with a history of habitual abortion of unknown etiology and to test the hypothesis that immunologic factors are involved. Fourty-four couples were taken into study. The overall pregnancy rate in the first subsequent pregnancy was 62%. Neither significant increased sharing of Human Leucocyte Antigens (HLA) nor an aberrant mixed lymphocyte reactivity in this group was found when compared to control random matings. The presence or absence of antipaternal antibodies did not correlate with the outcome of the subsequent pregnancy. It is concluded that the prognosis of untreated patients with habitual abortion is favourable and that no aberrant immunologic reactivity could be demonstrated by means of up-to-date diagnostic procedures.