I probably should have done this months ago since it’s really essential to understanding what my major malfunction is….Hang in there, it’s technical…

Under normal circumstances, humans have 46 chromosomes in each of the cells that make up their bodies. The complement of 46 chromosomes is composed of 22 pairs of ‘autosomes’ and 1 pair of sex (either XX = female, or XY = male) chromosomes – half of the total complement being inherited from each parent. Individual chromosomes are quite distinct in their appearance and most have long and short ‘arms’ that are connected by a structure called the centromere. When cells replicate to make another cell, they first duplicate their chromosomes and centromeres. The centromeres then connect to the structures in the cell that help separate these duplicated chromosomes from each other so that each new cell which results gets exactly the same chromosomal complement that was present in the ‘mother’ cell. This event is called mitosis.

To produce gametes (ova and sperm), a slightly different process is involved. Following duplication of the chromosomes, the overall complement of chromosomes delivered to each gamete mustbe reduced to half (23) that found in other cells in the body. This is two-step process called meiosis in which the centromeres also play a key role. During meiosis, the individual chromosomes (that were inherited from each of your parents) segregate more or less randomly into the resulting gametes, providing the great variability seen in our offspring.

Five of our chromosomes (13, 14, 15, 21 and 22) have ‘short arms’ that are very small and which contain no essential genetic material. These 5 chromosomes are called acrocentric chromosomes, or ‘acrosomes.’ Acrosomes have a tendency to fuse at the centromeres with other acrosomes, thus producing a ‘single’ larger chromosome made up of the ‘long arms’ of the chromosomes of origin, connected by a single centromere. When this occurs it is known as a ‘Robertsonian translocation.’ If no essential genetic material is lost (or gained) in the process, the individual with such a chromosome is said to have a ‘balanced’ translocation and appears ‘normal’ although they now have only 45, rather than 46, chromosomes in each cell.  That’s me.  I have one 13, one 14 and one 13/14 which are fused.  I’m not lacking any genetic material since the short arms don’t contain anything essential.  For what it’s worth, both boys were just like me.  We had to have an amnio done after the ablation and that’s when this was discovered.  The cell indicated that Baby B was exactly like me and therefore, Baby A, since they were identical twins, would have been too.  The translocation is not why they died.

Robertsonian translocations can occur between any of the acrosomes although this is not entirely random and the most common forms of these occur between chromosomes 13 and 14 (75%). Individuals with Robertsonian translocations can have these as the result of a spontaneous event occurring during the meiosis (in either parent) that produced the egg or sperm from which they were made, shortly after conception (called “de novo”), or from the inheritance of the same from one of their parents.  I don’t know which one I have.  I have no siblings so it’s hard to know if mine is “de novo” or inherited.  Doesn’t really matter for that reason, no one else, aside from my children will need to know this because there is no one else of child bearing age.

Robertsonian translocations are present in approximately 1/1,000 newborns. Individuals with balanced translocations are usually healthy and often unaware of their condition, especially if there is no prior family history that has led to the diagnosis, and often their chromosomal ‘abnormality’ will not be discovered until they have difficulty having children. The problem arises when individuals with Robertsonian translocations try to make gametes.  My gametes can have one of six scenerios:

1) One free copy of chromosome (chr) 13 and one free copy of chr 14.

2) The translocation (chr 13;14) chromosome alone (which contains one copy of chr 13 fused with one copy of chr 14).

3) Chr 13;14 + one free copy of chr 13 (essentially, a gamete with TWO copies of chr 13 rather than just one).

4) One free copy of chr 13 (and NO copy of chr 14).

5) Chr 13;14 + one free copy of chr 14 (TWO copies of chr 14 rather than just one).

6) One free copy of chr 14 (and NO copy of chr 13).

Obviously, 3 through 6 are gametes that have the incorrect number of chromosomes (either too little or too much genetic material). When these gametes get together with the, presumably, ‘normal’ gametes from Tim (which contain one free copy of chromosome 13 and 14), the following possibilities result (in the same order as above):

1) Two free copies of chr 13 + two free copies of chr 14 = NORMAL

2) Chr 13;14 + one free copy of chr 13 + one free copy of chr 14 = translocation ‘carrier’ (just like me) with NORMAL TOTAL amount of genetic material

3) Chr 13:14 + TWO free copies (one EXTRA from Me and one from Hubby) of chr 13 + one free copy (from Hubby) chr 14 = TRISOMY 13

4) Two free copies chr 13 (one from Me and one from Hubby) + ONE free copy of chr 14 (NONE from Me and one from Hubby) = MONOSOMY 14

5) Chr 13:14 + one free copy of chr 13 (from Tim) + TWO free copies (one EXTRA from Me and one from Hubby) chr 14 = TRISOMY 14

6) ONE free copy chr 13 (NONE from Me and one from Tim) + two free copies of chr 14 (one from Me and one from Hubby) = MONOSOMY 13.

Mathematically, I only have a 2 in 6 (33.3%) chanceof having a baby that has the right TOTAL amount of genetic material; one of these will be entirely chromosomally normal and the other will be a translocation ‘carrier’ just like me.  Two-thirdsof my babies are at risk for being chromosomally ABNORMAL.  This is how the geneticist explained it to me.  However, things are not quite that simple. Indeed, my actual risk for having a living baby with a chromosomal abnormality is much lower than this. The monosomy 13 and 14 embryos will not be successful at all (this is my 8-9 week miscarriages) and the trisomy 14 embryos also have very little chance of surviving much of the first trimester. Most trisomy 13 embryos will also be lost early in first trimester (this is my 5-6 week miscarriages) and the few that survive will have only a small chance of surviving the pregnancy and even a smaller chance of living more than a few hours or days after birth (we would know around 13 weeks if we had a Trisomy 13 fetus). These babies all have severe congenital malformations and if they manage to survive birth and the neonatal period, profound metabolic disturbances, and mental retardation. UNC has NEVER seen a living Trisomy 13 baby at birth.  I am aware that they do exist.

Some doctors argue that the ‘selective forces’ are so strong against these chromosomally abnormal conceptuses that at least two-thirds of pregnancies in which a pregnancy is actually confirmed will be chromosomally normal and the chances of actually DELIVERING a chromosomally abnormal baby are probably only about 1%!  That’s making the assumption that I don’t get a positive pregnancy test.  This is based on the argument that the pregnancy will end before I even know it’s happened.  That’s not the case with me.  I’ve been pregnant 6 times in 18 months.  I don’t need EPT to tell me when I’m pregnant.  I’m the Goddamn bloodhound of knowing when I am pregnant. 

So if you take out the instances when the pregnancy isn’t even “confirmed,” it appears that the overall risk of miscarriage is about 25% and this is the number doctors like to toss about. 

Makes me feel warm and squishy to think it’s only 25% but really, rational me knows that’s not the case.

Anymore questions, ask me, I’ll tell you…


28 Responses to “A Short Lesson in Genetics or What the Hell is Wrong with Me…”

  1. Tarah Says:

    From one balanced translocat-y to another – you did a beautiful job of explaining what’s going on.


  2. Kelly Says:

    This is a great explanation – thanks for posting!

  3. lillyshephard Says:

    great explanation…wow, i feel equipped to pass an exam after reading! and i’m sorry for your losses…loss after loss.

    wishing you all the best on your journey.

  4. Kate Says:

    Thanks for the explanation. I had no idea you had gone through so much. I know that people with CF carrier genes can sometimes go IVF route and seperate out the embroyos that have it and those that don’t. Can IVF, etc potentially do this? So they transfer only the embryos that don’t have the issue that causes miscarriage? I know its highly expensive and I at the moment am not in a budget to afford IVF I think, but I was wondering.

  5. Maricel Says:

    I will need another session to read this to be able to grasp the technicalities. 🙂 Seriously, I wish you well. I hope adoption will work out fine to you and your hubby.

  6. klboone212 Says:

    It’s weird i’ve always struggled in meiosis and mitosis concepts until I had my loss and I’ve now met so many other monthers who have lost and had genetic abnormalities. You did an excellent job of explaining this. I actually “get it”. Maybe I should try for that nursing degree that I really really want now?

    Anywho, I’m so sorry for your losses. Hugs.

  7. seda_algodon Says:

    Thank you for this explanation. I am just in the beginning of the process of figuring out what a balanced translocation is and what our options are for the future. We just moved and changed jobs, so we’ll wait to meet with a geneticist until our insurance kicks in.

    I’ve lost two babies in the last 8 months. One at 20 weeks and one at 23 weeks. We know the second had ring chromosome 13, the first we believe had the same thing because of her birth defects but they weren’t able to get a culture to grow to test her chromosomes.

    We seem to have a lot in common – both lived in LA, both worked for elected officials at some point in our careers, both have BT (actually I don’t know yet if it is me or my husband).

    I am glad I found your blog. You are a bit ahead of me in your journey, and I hope to learn from your experiences. We’ll consider adoption too, but right now we are focused on mourning the loss of two children in less than a year.

  8. Emma Says:

    Your explanation of BT’s is excellent here, I’ve been looking online for different sites about BT’s after finding out I have Robertsonian Balanced Translocation of the 13 and 14th chromosomes same as you have. I can really relate to all your blogs, I read them all and with a pain in my heart because it’s such similiar thoughts and sadness as I am having also.

  9. tasha Says:

    i have just recently found out that i am a carrier of rob 13 14 as well..we lost our baby boy at 23 weeks. im still recovering physically but we hope to concieve again asap…it is “nice” to know that i am not alone in this venture and that there are others that share similar stories..my heart goes out to each and every one of you..we have a genetic council meeting next week and was wondering if there is anything you would suggest regarding questions? it breaks my heart to hear your story as we want nothing more than to have another child…this is a scary journey as im 34 and dont really have time on my side to try and try again…this was our first time getting pregnant…so much to ask so much to learn so little time…would love to hear of anyones story..much love to us all..xoxo tash

  10. ALICIA Hall Says:

    I loss my son Aidan almost three years ago at the age of 8months. He was born with down syndrome happiest baby ever i must add. He passed away after heart surgery. I was told after he was born that he had robersonian trans-location and i should be tested but i declined . I didn’t want it to be my fault my son had DS. But i have matured and have grown and now im curious . Thank you for sharing i kind of understand it a bit clearer . Thank you

  11. rachael Says:

    Hi I have the same condition, I am on my 5th pregnancy (previous 4 all lost) I am really looking for some kind of hope that I actually stand a chance of having if not this baby then one in the future….anyone know of any happy successful stories?????

    • sally Says:

      hi Rachael and everyone on this journey, I have a happy success story! I have a balanced 13 14 translocation and after 2 miscarriages (maybe some unknown) I went on to have 2 healthy strong children, now 14 and 13 years old. I was 37 and 39 years young when i gave birth! I hope that inspires you, lots of well wishes and hugs.

    • Paula lupr Says:

      Hello. I have posted my story. Just a little hope for you. I was told that I have 2 translocation, and that I would not have a living baby. I gave birth to a little girl in 1993. She is now 19 1/2 years old and in very good health. She is a normal young lady and in college to become a nurse. So sorry for your loss. I had 7 miscarriage before I had her. I feel sadness. Paula

    • Christina Says:

      I have this condition and have three beautiful, healthy boys. I had three miscarriages as well. Stay positive!

  12. rachael Says:


  13. Mindy Says:

    Great Explanation! I have balanced translocation of 13/14. had 4 miscarriages in a row. Did 2 rounds of IVF with PGD which failed 😦 then I had a lucky streak. 2 healthy baby girls in a row and due with my son any day now with no miscarriages since 2004. It can happen!!!

  14. Tasha Says:

    Well, it has been a couple years now since I have read and/or responded to this blog. Since the loss of our son in Nov 2009, we carried him to 23 weeks and through ultrasound found out he was not compatible with life and at that point we had to make the decision to end his precious little life through a procedure in which stopped his tiny malfunctioning heart. A day later we went in to labor and delivered our stillborn son. Hands down the hardest thing we will ever have to go through and not a moment goes by that we don’t remember and honor the life in which our son did have inside my safe, warm belly. We miss him dearly but know we made the right decision for us. We are now on our 5th pregnancy in 2 years with no living children. We have lost them all before our 9th week of pregnancy and with tissue samples from all we have found out that they all carried trisomy 13. We had made the choice to continue trying naturally until the end of my 35th year which was the end of 2011 and happily so we found out right before New Years Eve that we were pregnant! We are 7weeks on Monday and have our first ultrasound on Wed 25. I will keep you all posted as to how it goes. We are holding strong to the fact that this little one will decide to stick around for the long haul but reality speaking, if he/she decides to have a different journey then we will be considering IVF as we don’t feel we can healthily endure this any further….It takes such a tole on your spirit….Happy thoughts to each and every one of us!

    Much love,

    Tasha xxx

    • Markitta Says:

      Hello. I have just lost my first child at 14 weeks 3 weeks ago because of robertsonian translocation. By far the most devasting event in my 33 years. A lost and void that I am only starting to surface from. We came in for a routine check and discovered his little heart was not beating. After testing they discovered this genetic abnormality. My husband and I are waiting for our genetic test results to return. I understand that there is a chance it could have been spontaneous or usually from the mother. I want to keep trying naturally but the lost of my little one is so hard to bare at times. I’m glad I found this blog cause it gives me hope. Thank you for posting and for all those who replied as well as the eloquent explanation of the condition. Were you ever successful in carrying a child to full term naturally?

  15. Tasha Says:

    Ps: Congratulations Mindy!

  16. mickeala Says:

    Hi, i am 4 weeks preg on my 6th preg, i’ve had 5 prev m/c i also have trans 13/14 chromo. Did u have your children naturally?

  17. hi,iam a36 year old male and i did chromosomal analysis and report was as follow:chromosomes of 15 cells from cultured preparation were counted and analysed using G banding,all showed 46 chromosomes including sex ch.all metaphases showed a balanced translocation between the long arm of ch.12 and the long arm of ch.13
    for my wife was normal and karyoyyping 46XX

  18. Tony Says:

    Thank you for this concise technical description, it saved me the hassle of hassle of reading more verbose documents 🙂

  19. Brie Says:

    I also have a translocation – I am 13;14. I had genetic counselling when i was 19 years old. I am now 28 and more interested than in the past, in the probability of conception. Thank you for posting this, i rarely find informative postings from people who are in my position. I am still confused about the whole scenario but hopefully I will soon figure it all out!

  20. Paula lupr Says:

    In 1992 I had my 7th miscarriage, I was sent in for translocation testing. I have two translocation. I was told that I could not have a living baby and if I did that it would not live past the age of 2. University of Michigan told me this. Well I am proud to share some ray of hope to my translocation family. I have a very healthy 19 1/2 year old beautiful girl. I am so sorry for everyone loss. I do know your pain. But I hope this gives you all a bit of faith.

  21. david Says:

    Excellent explanation! I’m a medical student and couldn’t find a lucid description of whether or not the Robertsonian translocation was occurring each time your oocytes are undergoing meiosis II (unlikely), or whether it had occurred during your own conception (or your ancestor’s for that matter – might account for your comment that you haven’t got any siblings?). Your explanation made the point very clearly, so thank you.

    Anyway, I’m also a father, and I’m sorry for the pain you must be experiencing with such hopes. Sadly, we lost our first one at about 8 weeks gestation, so happily, our 10 month old son has a little sister praying for him and for me, who needs all the prayers he can get to pass the USMLE! Speaking of prayers, St. Gerard Majella is the patron of expectant mothers, so if it’s a miracle you’re looking for, he’s the guy.

    Again, thanks for illuminating the obscure.

  22. Ashley Says:

    I am a balanced robertsonian translocation (13 : 14 ) i found out in 2010 when I was pregnant with my first child who I found out had trisomy 13 I carried her to 39 weeks and she was born but alot of health problems she passed away at 9 days old we then tried again had a miscarriage. But on our 3rd try we have a son who is now 2 never had a health problem but is a carrier like me . I was the only one in my family to have this no history. It has been really helpful to hear about someone else’s experiences

  23. Cheryl Says:

    Just came across this blog, wondering how everyone was getting on ? My daughter found out that she was a carrier of a balanced 13:14 Rob translocation after suffering 2 miscarriages and having to terminate a pregnancy at 16 weeks due to the baby having an unrelated condition that was incompatible with life. (very bad luck) On the plus side she has a 9 year old son and a 2yr old daughter, we don’t know if they are carriers and she is presently 8 weeks pregnant and undergoing regular scans but obviously worried silly.
    I also had the test which found that I was also a carrier with a result identical to my daughter of 45, XX,der (13;14) q10;q10. I hope this gives some hope as I have had 5 gorgeous children, all now grown up, eldest 32, youngest 18, I had 2 miscarriages after my first child, then a year of infertility, I then conceived twins after a course of clomid, but I lost a twin at 8 weeks the other twin survived, I then had a 3rd child no problems at all, My 4th child caused a lot of worry as I bled for 4 months, but born healthy I then miscarried my next pregnancy and then my youngest was born after a 4 year gap, obviously I didn’t know of this chromosomal problem as no test is done until you have 3 failed pregnancies in a row so I feel extremely lucky to have my large family. So far only two of my children have had the test, the one I have mentioned and my 4th child a daughter who has been trying for a baby for 10 months with no luck, but she was found to be normal (46 XX). The others can have the test as and when they want to, so all I can say to you all is Never give up!!! Good luck

    Cheryl x

  24. Ashley Says:

    I no unfortunately that I was born with a balanced 13:14 but I have a two yr old carrier like me who was born 9 pounds healthy as a horse but he was also my forth pregnancy and I have no other children other then him but there is hope four pregnancys later, we got a beautiful healthy baby who we thank god everyday for. We are now thinking of trying again for a second child but its a scary lengthily process but I am proof that you will have a healthy baby u just have to be strong and keep trying

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