This is a transcription of a portion of a Healthful Woman podcast.
Rena’s Question
Our next question is from Rena. “Would you be able to include in one of your podcasts the topic of balanced translocations? For example, how common is it, how it affects fertility or treatment options or lack, if diagnosed, is it more common in men versus women? In other words, will my future sons or daughters be more affected by it, and anything else you could share on the topic? Much appreciated.”
Dr. Fox’s Response
All of us have 46 chromosomes, typically arranged in 23 pairs. A translocation happens when a piece of DNA breaks off one chromosome and a piece breaks off another, and they get flipped, so DNA from one chromosome ends up on the other and vice versa. There are two kinds: balanced, where the overall amount of DNA is correct even though it’s in the wrong spots, and unbalanced, where DNA is actually extra or missing.
Here’s an analogy I like. Imagine you have two full sets of a 26-volume encyclopedia in your house, one set in the study, one in the bedroom. If you swapped the Uruguay volume from your study with the Lennon volume from your bedroom, and put them back in the wrong sets, you’d end up with one set that has two U’s and no L’s, and one set with two L’s and no U’s. Overall, you still have 52 books, two complete sets. That’s a balanced translocation. An unbalanced translocation would be if you lent out your Uruguay book and got back an extra Lennon book instead, leaving you genuinely missing a volume.
For most people, a balanced translocation causes no illness at all. They’d never know they had one unless specifically tested, since every cell still has the right total amount of DNA. There are rare exceptions where certain balanced translocations raise the risk of specific conditions, including one particular type of cancer, which is one reason genetic counseling matters when a translocation is identified.
The issue comes up in reproduction. When you pass along only one set of your 23 pairs to a child, and one of your sets has extra DNA in some places and missing DNA in others, your child may inherit an unbalanced set, too much or too little DNA. Unbalanced translocations are a well-known cause of recurrent early miscarriage, which is why testing parents for a balanced translocation is a standard part of the workup after multiple losses.
Overall, it’s fairly uncommon. Even among people with recurrent miscarriage, it shows up in roughly 2% to 3% of cases, and it’s less common still in the general population. It doesn’t typically affect fertility treatment options beyond needing IVF with embryo testing, since hormonal treatments to help with ovulation won’t address the underlying chromosomal issue. For the vast majority of people who carry a balanced translocation, life goes on completely normally. For those who do experience related miscarriages, testing and family planning support can make a real difference in the path forward.
Learn More on the Healthful Woman Podcast
Dr. Fox answers several other questions in this episode, including why twins require a different delivery approach for the second baby than a singleton breech birth, what a fetal heart arrhythmia picked up on a routine visit usually means, how a high fetal fraction on prenatal genetic screening relates to fetal growth, and whether there’s a safe upper limit on the number of C-sections a person can have. To learn more, listen to Mailbag 31 on the Healthful Woman podcast. If a question like Rena’s applies to you, Carnegie Women’s Health offers genetic counseling and cancer genetics testing with Laura Mueller, our genetic counselor, as well as family planning services to help you weigh your options. You can request an appointment with our team any time.
Carnegie Women’s Health blogs are intended for educational purposes only and do not replace certified professional care. Medical conditions vary and change frequently. Please ask your doctor any questions you may have regarding your condition to receive a proper diagnosis or risk analysis. Thank you!
