I'm sure it does cause potential complications to an extent. However, I know of at least two comparable situations that occur without medical intervention: 1)

I'm sure it does cause potential complications to an extent. However, I know of at least two comparable situations that occur without medical intervention: 1) Pregnant women -- During pregnancy, and to some extent afterward, the mother's blood contains cells from the fetus she is carrying. Some of these cells migrate to other places of the body. Scientists hypothesize that this is part of why pregnancy may lower cancer risk -- something about how the mother's immune system deals with these foreign cells. This is called fetal microchimerism. http://www.scientificamerican.com/article.cfm?id=fetal-cells-microchimerism http://www.scientificamerican.com/article.cfm?id=fetal-cells... 2) Chimeric people. In rare cases, a human can be born that is made up of two separate DNA profiles. http://en.wikipedia.org/wiki/Chimera_(genetics) http://en.wikipedia.org/wiki/Chimera_(genetics)