I often see a lot of threads here on BH from people who are newly pregnant/TTC/ just hoping for twins in general asking what they have to do to conceive twins OR that because twins run in their family are they a higher chance of conceiving twins.
So, I thought I would start a thread and lay down some facts and maybe dispell a few myths along the way. If you have anything to add, feel free to do so
I am going to close this thread and keep it closed until I have finished with all my posts, and then I will open it all for comment, or for you to add your own pieces.
To keep it easy to read, each new subject/idea will be put in a new post
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Results 1 to 10 of 37
24-05-2010 10:32 #1
Twin Genetics - ID/frat, Are you a chance of having twins etc
24-05-2010 10:39 #2
Do Twins Run in families?
This is probably one of the biggest myths out there. If I had a dollar for everytime I asked "do you have twins in your family?" I think I would be close to a millionaire. (Well, a girl can dream )
While some families do seem to have a multitude of multiples, it's most likely more of a coincidence than a connection.
Certainly, with fraternal twins (two eggs released at ovulation and fertilised) it may be a case of hyper-ovulation; the tendency to release multiple eggs during ovulation. So, in a family where women have the gene for hyper-ovulation, it may be passed on from one woman to the next (hence, many twins in that family).
Because only women ovulate, this gene is only relevant on the maternal side of the family. Although there is a school of thought that suggests men can carry the gene and pass it on to their daughters. If this is true though, if someone came up and asked you if you had twins in your family because you have twins now, and you only had them on the fathers' side, it is irrelevant that there are a history of twins there or not.
Identical twins (monozygotic = one egg that seperates) is entirely a freak of nature, and no one knows for sure why it happens. It is thought that it is more prevalent in both IVF babies and older women, as these eggs are less stable.
24-05-2010 11:06 #3
So... am I a chance of having twins?
Taking in all of the above, if you want it broken down into easier to understand terms,, consider these factors:
What kind of twins are in the family?
If they are fraternal (dizygotic) twins, there is a faint possible yes.
Remember, ID (monozygotic) twins are random.
Are the twins in your family a result of assisted reproduction?:
Then no, you are not at an increased chance. With IVF and other assited reproduction methods, there has been a rise in the number of multiple births. But consider this: If your cousin was taking clomid and ended up with twins, then that would have no impact on YOUR ability for twins.
Whose side of the family has the twins?
Remember- hyper ovulation can only occur in women. Therefore, if the maternal side of the family has a history of fraternal twins, then you may be in for a chance.
If it was your fathers side (paternal) kiss that twin idea goodbye, as twins for you will be random.
Other factors to consider:
Maternal age, race, weight, diet, reproductive history (including use of assisted reproductive technologies)
24-05-2010 11:27 #4
What is all this monozygotic/dizygotic stuff: Understanding your twins zygosity
You will have noticed I started to refer to twins as monozygotic and dizygotic. This is mainly for one reason: my boys we are 80% sure* are monozygotic. That means they are 'identical'. The word identical does not describe them though. You can have two babies from the one egg and not have them be EXACTLY the same. There are even some (rare) instances of two babies from the one egg being boy/girl twins.
*Only 80% because to know for sure I would have to get them tested. Although- they shared a placenta, which accounts for the 80%, but had seperate sacs (which throws in that 20% uncertainty)
One zygote, or egg.
This means two babies from one egg. The egg splits apart within the firs few weeks of conception. No one knows why. Hence MZ twins being completely random. The twins share the same DNA split, although sometimes within hours of the split, the DNA in one or both feotuses can morph.
MZ twins are commonly referred to as identical, but this isn't always the case. They may share VERY similar looks and personalities, but because there are so many outside factors as to what makes up a person, MZ twins are very much their own person. MZ twins can sometimes look very different, and as stated above there have been some b/g monozygotic twins.
Two eggs released and fertilised.
The genetic connection is no more or less than to two siblings conceived and developed years apart. Two eggs are released upon ovulation, and are both fertilised by the father. They grow and develop in the womb together, most likely with their own placenta. (Although placentas can fuse to make one) DZ twins may look alike, but then again may be entirely different.
How can I determine my twins' zygosity:
The only sure way is DNA testing, since relying on if they look the same or not isn't foolproof.
There are some indicating factors that I have hinted to above, but remember every rule has it's exception.
*If your twins shared 1 placenta and one sac, they are most likely monozygotic. They are referred to as monochorionic monoamniotic twins. (Meaning they shared a placenta or chorion, and a sac or amnion)
* If your twins shared 1 placenta but had their own sacs, again they are most likely monozygotic, but like I pointed out above there is about a 20% chance they are dizygotic, and have fused two placentas to make one. These twins are referred to as dichorionic monoamniotic twins.
*If your twins each had their own placenta, they are most likely dizygotic. They are referred to as dichorionic diamniotic twins.
*If your twins are boy/girl, they are most likely dizygotic... the chances of having b/g mz twins are something like 1 in 10,000 (I think- it's some insane number that I can't recall off the top of my head and would have to delve into my research to remember.)
In the end though, it doesn't really matter what zygosity they are- they are your children and they are beautiful
(ETA: an excellent way to see all these points laid out infront of you is in this zygosity chart I just found, thanks to about.com
Last edited by Mod-Nomsie; 24-05-2010 at 14:09.
24-05-2010 11:40 #5
So... I think that is the main stuff covered... if there is anything you would like to add, go ahead... or if I have missed something or gotten something wrong, let me know. This is all just stuff I have picked up whilst reseraching multis when pregnant so some of it may have gotten a little skewiff in my brain
24-05-2010 12:07 #6
Good thread! If you dont mind me adding my bit, something my ob told me about monozygotic twins might be of interest to us all.
If the fertilised egg divides before day 5 (after ovulation), the resultant twins will each have their own placenta and sac, as the 'splitting has occurred before implantation into the womb has generally taken place. This accounts for up to 40% of monozygotic twins and explains why some parents cannot understand why their twins look exactly the same when they had separate placentas.
If the fertilised egg divides between days 5 to 8 the twins will each have their own sac but will share a placenta, as the implantation process will have started. This accounts for approx 80% of mono twins.
If the fertilised egg divides between days 8 and 12 the twins will share a sac and a placenta. This accounts for only about 2% of mono twins and these pregnancies are very high risk as there is a much greater chance of the cords becoming entangled or twin-to-twin-transfusion syndrome occurring.
In the fertilised egg divides after day 12 conjoined twins will result, who will also share a sac and a placenta. Fortunately, these are very rare.
24-05-2010 12:54 #7
Thanks Ladies ...you backed up my research and what my Ob said
Nomsie - i get the "does twin run in your family all the time" i just say nope i did IVF that usually shuts them up ...mine are Monozygotic and i get ask how i know they are ID before they are born and again i use the cause we only had one egg put back
and then think to myself unless DH became a freak and regenerated his missing genes there is no other way lol
Thanks again great thread
27-05-2010 18:27 #8
Chances of tripets-
1:250,000 of ID triplets. 1 egg split into 3
1:8000 of fraternal triplets. 3 eggs
1:10,000 of ID/fraternal mix triplets. 2 eggs, 1 split.
27-05-2010 18:30 #9
BGBGBB - 8-12 day egg spliting results in MoMo twins, not mono.
27-05-2010 21:56 #10Senior Member
- Join Date
- Oct 2008
If not, how do you get one male and one female bub from one egg and one sperm? The sperm would be either male (contains Y chromosome) or female (contain X chromosome).
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