Human immune system works in a remarkable way. It guards our body in such a way that no exterior body can ever penetrate the strong defenses of the immune system. Even if it does, there is a whole army of antibodies ready to attack the foreign body. The substance which triggers the formation of antibodies is called an antigen. It could be anything right from a part of bacteria, virus, pollen or any toxin. Even other person’s blood can trigger antibody formation in our body. However, formation of antibodies in blood is not always a desirable thing. It could be particularly dangerous during pregnancy under certain circumstances. Before we delve deeper into the relationship of blood antibodies and pregnancy along with immune system function, let us know more about them.