Remember chromosomes occur in pairs in all cells except sperm and eggs. If part of one chromosome is found connected to a completely different chromosome it's "translocated". For that person there is no net gain or loss of genetic material, so the translocation is "balanced" and there is no problem. But when that person makes eggs or sperm, some of these will have too much or too little genetic material. The same will be true for an embryo that results. The chromosomal translocation will then be "unbalanced" and the embryo will sooner or later usually result in a miscarriage. If the two particular chromosomes have swapped parts, we call it a balanced reciprocal translocation.