monochorionic twins.. identical?

This is the part that really really confuses me. putting placenta aside because of the fact that the placentas can fuse or be very close together.. if you have Mono/di twins..are they identical or could they be fraternal? And if they can be fraternal what are the %'s

I mean.. I get mono/ mono are identical 100%.. and di/di can be either fraternal or identical.. but the mo/di thing has me :huh:

 

Mo/Di twins are identical. I believe the first "mo" is monozygotic, meaning from one egg. The second "mo" or "di" would be monochorion or dichorion, meaning one or two sacs.

 

monozygotic..thats a totally new word to me.. now I need to find more info on that.. lol..

 

OK.. I lied... I knew it didn't sound right when I hit post!

Anyway, monozygotic is the technical term for identical twins, meaning from one egg.. It has nothing to do with the mo/mo, mo/di, di/di combinations..

The first mo is for monochorionic (I'm sure that is spelled wrong), which I think means one placenta.. If it is truly one placenta, and not fused - then they are ID twins.

Sorry.. It's been a while since I read all this stuff - my girls are VERY fraternal!

 

no problem.. really you helped me a ton because when I put in monochorionic into the search box I got a million posts to look through.. but I typed in monozygotic and bam.. like 7 posts and got this info.. so Thankyou very much for your help.

Identical Twins
With identical twins, one egg (zygote) from the mother is fertilized by one sperm from the father, and then very early in development the embryo splits and two fetuses grow.

If the zygote splits very early (in the first 2 days after fertilization) they may develop separate placentas (chorion) and separate sacs (amnion). These are called dichorionic, diamniotic (or 'di/di') twins. While all fraternal twins are 'di/di', this occurs 20 - 30% of the time in identical twins.

Most of the time in identical twins the zygote will split after 2 days, resulting in a shared placenta, but two separate sacs. These are called monochorionic, diamniotic ('mono/di') twins.These twins are very similar genetically, and share a single afterbirth.

Very occasionally, twins will also share the same sac (fluid cavity). In about 1% of identical twins the splitting occurs late enough to result in both a shared placenta and a shared sac. These are called monochorionic, monoamniotic ('mono/mono') twins.

Finally, the zygote may split extremely late, resulting in conjoined twins.

 

oh.. and I looked up monochorionic for a definition..

Definition: When monozygotic twins are contained in a shared chorion, they are referred to as monochorionic. The chorion is the outer membrane of the sac surrounding a fetus in utero. Monochorionic twins can be either monoamnionic or diamnionic.

 

A few little corrections: the zygote is not the egg (that would be the oocyte) but the very first thing that is formed when the egg and sperm fuse.
Mono/di twins are not "very similar genetically" they are identical genetically!
And yes everything else was right, Millie (the expert, who has read aprox. 17 papers on identical twins just today... for research, I am working on a paper on TTTS)

 

Thankyou Millie.. I was really curious as to whether my twins were being said to be identical because they were monochorionic.. or because of the placenta..Sounds like they are idential either way and i can only hope that they have fused placenta's that look like 1.

 

Mel, I think you were on here quite a while ago thinking you were possibly having twins but it ended up being just one baby. So now you ARE having twins? Wow...congratulations! How early did you find out that it looked like one placenta? If determined fairly early on, it most likely IS one placenta and not two fused.

 

Hi Melissa.. yes.. I was on at the beginning of my last pregnancy asking about disappearing twin. At my first u/s with that baby they had found 2 sacs but only 1 baby. They were never able to confirm the 2nd baby as by the time I went back to my 2nd u/s it was gone. I did wonder after that if they could have been missing the 2nd baby. Isabellah is 10 mo old now. I had a different name though and can't remember what that was (mommytomany or something like that)

And yep.. pregnant with twins. Found out at 11 weeks..this is also when they checked the placenta. I posted the u/s pictures in my first post. This is the only one of them in the same sac..kind of like looking from above them.

http://farm3.static.flickr.com/2365/221751...4869bd6b0_b.jpg

I will post more on monday after my next u/s

 

So if there is 2 different placentas it doesn't mean that they aren't id right? I have 2 different placentas and am wondering if they could be faternal or id. I thought they would be faternal. Am I right?

 

Do your twins share the Chorion or have 2 seperate Chorions?

They can be identical or fraternal if they have 2 Chorions/ 2 amnions.. or other wise known as di/di twins.. If they share a chorion they are Identical even if they have 2 placentas.. atleast I think I have that right.

 

WOAH!!! haha I learned alot.... All I really know is that my babys are Identical, they share a placenta, and their is a really thin membrane between them. It think their Mo/Di or something not sure.

 

I fall into the 1%.