What is balanced translocation?

A balanced translocation means two chromosomes have exchanged segments, but no genetic material has been gained or lost. Everything is present — just rearranged. Because nothing is missing or extra, a carrier is typically healthy and usually has no idea until investigation for recurrent miscarriage or difficulty conceiving reveals it. There are two main types. A reciprocal translocation involves an exchange between any two chromosomes. A Robertsonian translocation involves two of the acrocentric chromosomes joining, most often chromosomes 13, 14, 15, 21 or 22. The reproductive consequence comes from how these chromosomes separate when eggs or sperm are formed. Some resulting eggs or sperm carry the correct amount of material; others carry too much or too little. Embryos with an unbalanced complement usually fail to implant or miscarry, though some can result in a live birth with significant problems, depending on the chromosomes involved. Two things worth knowing that couples are often not told: Live birth rates without any assisted reproduction are as high as 70 to 71% in observational studies of translocation carriers, with miscarriage rates of 29 to 30%. Finding a translocation has implications for your relatives. Siblings and parents may carry the same rearrangement, and would benefit from knowing before their own pregnancies. Genetic counselling should include discussing how to inform family members. The specific chromosomes and breakpoints involved determine your individual risks, so ask for counselling specific to your rearrangement.