Received April 14, 2007
Accepted June 01, 2007

This paper reviews the alloimmune factor of the recurrent spontaneous abortion (RSA).It is based on literature accomplished in publications of the last 10 years(1997-2006),researching the data of bases OVID-Medline,Science Direct and Lilacs and the search sites Pubmed,Bireme,Google. Results:The recurrent spontaneous abortion(RSA) is defined as the loss of 3 or more consecutive gestations,clinically detectable,before 20 weeks of pregnancy or less than 500grams of the weight of the fetal body.It could affect up to 5% of the fertile couples.Approximately 50-60% of the spontaneous abortions are due to genetic causes,however,abortions in women with RSA have a low incidence of genetic abnormalities.Some authors suggest that the cause of idiopathic RSA is autoimmune or alloimmune in 50-60% of the cases,and the involved mechanisms include presence of antibodies cytotoxic,absence of maternal blocking antibodies, increased sharing of antigens HLA, hyperactivity of cytocins Th-1 and disturbances in the function and distribution of the cells NK.The term alloimmunity refers to the immunological differences among individuals of the same species.The hypothesis is that the antigenic maternal-embryonic difference would be beneficial for the development of the embryo.The maternal-embryonic histological compatibility can take to defects in the interaction mother-embryo, impeding the production of humoral and cellular factors of vital maternal origin for the success of the pregnancy. Conclusions:RSA constitutes a 5% obstetric occurrence.Although most of the recent studies on immunotherapy show encouraging results, controversies exist on the subject.The immunotherapy constitutes a therapeutic option with good results if accomplished a complete investigation protocol and correct indication.Multicentric placebo-controlled studies are still necessary for larger explanations.