translocation is a change in chromosome structure in which
chromosomes are attached to each other or pieces of
different chromosomes have been interchanged. An individual
with a translocation is unaffected if there is no extra or
missing chromosome material and if the break in the
chromosome did not disrupt gene function.
If there is no
additional or missing chromosome material, the translocation
is considered to be "balanced." A translocation is
"unbalanced" if there is extra or missing material.
Individuals with balanced translocations typically have no
medical issues though some do have fertility concerns, such
as reduced fertility.
The concern regarding having a
balanced translocation is that, though the individual is
healthy, the egg or sperm of that individual can have an
unbalanced chromosome make-up that leads to the resultant
embryo or pregnancy being unbalanced.
The presence of an
unbalanced translocation can lead to an embryo not
implanting, a pregnancy being lost or a child being born
with mental and physical problems. Individuals with a
translocation may, therefore, experience multiple pregnancy
losses or have a child affected with physical and mental
problems that may be lethal.
It is known that approximately 3 out of 4 (75%) embryos
created by IVF will not be capable of producing a live born
child. Some will fail to implant in the uterus, while others
will implant but are unable to carry out early embryonic
Finally, as in natural pregnancy, approximately
15%-20% of conceptions will be lost as a clinical
miscarriage. These numbers are often higher when a member of
a couple carries a balanced structural rearrangement.