Immune Function and Recurrent Pregnancy Loss

Recurrent pregnancy loss (RPL), defined as two or more consecutive miscarriages, is attributable to multiple causes. However, in 50% of cases no known cause is found. Although endometritis is a known cause of miscarriage, other inflammatory processes may play a role in idiopathic, recurrent loss. The fetoplacental unit evades rejection by the maternal immune system by poorly understood mechanisms. Despite this seemingly immune-privileged state for the fetus, human implantation requires inflammatory mediators for attachment and implantation. This review describes how the immune system must simultaneously permit and restrict trophoblastic invasion for healthy implantation and maintenance of pregnancy. Included in this review is a detailed description of the immune milieu in the decidua and abnormalities that are associated with RPL. Finally, autoimmune states associated with RPL and their treatment in an obstetrical setting are reviewed.