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The job of the immune system is to protect the body from infections caused by foreign cells. Under normal circumstances, viruses, bacteria and other pathogens are identified and fought by white blood cells.

When the embryo is implanted, cells that carry the father’s genetic material enter the female body, similar to a transplant. As an immunological reaction to this, from the moment of implantation the woman starts producing a protective shield for the baby – so called Fc-blocking antibodies. These antibodies surround the embryo like a protective cover and make the child ‘invisible’ to the mother’s own immune system.

It is important that the mother’s immune system ‘recognises’ the embryo so that it can start producing the Fc-blocking antibodies. If not enough Fc-blocking antibodies are formed, there is a high probability the embryo will be rejected by the mother’s immune cells (killer cells) during pregnancy.

Studies have shown that the mother’s immune reaction is too weak, and the production of Fc-antibodies is inadequate when the cells of the mother and father are very similar.

On the other hand, the implantation of the embryo can also trigger an overreaction of the mother’s immune system. In doing so, the immune system produces large amounts of killer cells in a short amount of time and these fight the embryo and greatly increase the risk of miscarriage.

Autoimmune diseases are rarely the reason why the embryo cannot develop further in the maternal body. Anti-phospholipid syndrome (APLS), systemic lupus erythematosus (SLE), multiple sclerosis (MS), ulcerative colitis and Crohn’s disease are common autoimmune diseases during a women’s reproductive years.

About 10 per cent of childless couples suffer what is known as unexplained infertility. A small proportion of these have an autoimmune disease (SLE or APLS).