Were/are your twins in one sac?

I had my NT scan today, and everything seemed well - but they couldn't really tell if there were two placentas close together or just one - and they couldn't see a membrane between the babies. We're going to have another u/s at 16 weeks to see if we can tell.

In the meantime, what was your pg like if they were in the same sac? Does that automatically mean identical? And, did you have any complications? If so, what happened and what did they do?

Here are some pics to give you an idea...

http://i2.photobucket.com/albums/y2/colofisch/12week2.jpg
http://i2.photobucket.com/albums/y2/colofisch/12week1.jpg

Jenny

 

Mine are in different sacs. I had an ultrasound at 10 weeks and the different sacs were very visible. Yours looks like the same sac but I am not a doctor or anything.

 

Our u/s was at 7weeks 5days when we learnt it was twins. You can very clearly tell they are in different sacs.
We had another one at 12weeks 2days and we weren't able to see both babies at the same time on the screen unless they were in the 3/4D view but you can clearly see the membrane.

First one is 7w5d
http://i3.photobucket.com/albums/y85/kamieshui/7w5d.jpg

Next two are 12w2d
http://i3.photobucket.com/albums/y85/kamieshui/baby6.jpg
http://i3.photobucket.com/albums/y85/kamieshui/baby4.jpg

 

One sac usually does mean identical. I found out I was having twins at 15 weeks and for the first couple weeks they couldnt find a membrane seperating them but then one day it was there but wasnt always so easy to find I think I was 19 weeks when they finally found it. In most of our ultrasound pictures it looks like 2 babies in one sac you cant really see the membrane. I was put on bedrest at 23 weeks because my bloodpressure was preventing them from growing. We suffered from TTTS but it happened at 32 weeks, had one amnio reduction, constant NST's and 3-4 ultrasounds a week. We made it to 35 weeks 4 days until Pre E became very seroius. It was a dificult pregnancy but they monitor you so much when your having twins, I am so greatful to have the technology that we have now.

 

It is my understanding that if they are in the same sac they are identical, and it is a higher risk pregnancy. BUT, sometimes it is really difficult to see that dividing membrane, even after several u/s.

 

As others have mentioned, that membrane between the two sacs can be tough to see in ultrasounds and will even be tougher to see as the pregnancy progresses. Keep in mind the word 'sac' can refer to the types of sacs, an inner sac (amniotic) or outer sac (chorionic) If the twins are in the same amniotic (inner) sac, they are identical, but this is fairly uncommon. If they share the same chorionic (outer) sac, they are also identical, but it is a much less risky type of twin pregnancy than monoamniotic. I really don't think people can tell these differences from basic ultrasounds, the separating membrane is just too tough to spot. When a doctor tells a patient it appears that her twins share one sac, a good question I always feel should be asked is what sac is she talking about (sometimes just so the patient can reassure themselves that their doctor is really up on the biology of a twin pregnancy).

To my uneducated eye, the ultraounds shown in the first post in this thread appear to be in one chorionic sac, but there's no way of knowing whether they are also in the same amniotic sac.

 

I totally agree with the PP. The term "one sa" definitely needs to be defined. My identical twin boys share a chorionic sac but the amniotic sac has a dividing membrane, resuting in two amniotic sacs, not mo/mo twins. Every time my doctor does the scan she is amazed at just how thin the membrane is. She had me worried that one of them could just punch right through it! But so far so good .

I hadn't had any problems regarding them being in one sac other than her constantly warning me about the dangers of TTTS. But recently (about 31.5 weeks) babay B slowed down in growth. When I went to the doctor yesterday, the u/s showed that he's trying to catch back up, but now baby A is slowing down! She doesn't seem worried but she definitely wants to deliver at 36 weeks. Good luck and make sure to ask which "sac" she is referring to.

-Larami

 

If they truly share a chorionic sac, they ARE identical. Fraternals can't share a chorionic sac. The only thing fraternals can have is the "shared placenta" look because their placentas fused. Even then, there should be no sharing of anything as there is a membrane that separates the placentas and doesn't allow connections (though there has been one instance of fraternal twins sharing connections -- there had to have been a problem with each placenta for this to happen). Only 1% of all identical twins share an amniotic sac -- about the same number as there are conjoined twins. Hopefully this isn't the case for you -- most women who first hear it might be monoamniotic twins eventually find a dividing membrane. The membrane is VERY thin and hard to find so don't stress about it yet. You can find support also at www.monoamniotic.org.

 

Both of my sets of twins, were in visible different sacs, two placentas, the whole nine yards. But a couple of my friends, were pregnant right along with me during the last and all having twins. Both of theirs were sharing a sac, and one shared a placenta. One delivered at 31 weeks the other at 32 weeks. Both had fairly smooth pregnancies tho, my pregnancy was more traumatic then what they had. So i guess really all of that depends on the person really?

But i do know, that one set was mirror image, and the others were identical.

 

Yep, mine were in 2 sacs. Here is a pic at 10 weeks of my guys...

 

They could not find my dividing membrane for a while. It took a couple of techs to find it. When they did find it they said it was very thin, I weas just happy that it was there. It is my understanding that if there is no seperating membrane then you have a very high risk pregancny. There is a risk of the two cord tangling. Form the pics it looks like yours are identical, your pics look like mine did. However I had 2 placentas ( they think that they split) and one sac with a thin membrane. It can be so confusing. Anyways congratulations.

 

The membrane might be hard to see, but it could be there. Otherwise to my understanding, twins that are in 1 chorionic sac and 1 amnionic sac are identical. Twins that share 1 chorionic sac, but have their own amnionic sac with the membrane seperating them,like mine, can be either identical or fraternal.
Mine also either share a placenta, or it fused really early on. I guess we will have to wait and see, if they are ID or frats.

Here is pictures of my ultrasounds
http://schultztwins.aboutmybaby.com/photoalbum/79870

Juli

 

One sac usually does mean identical. HOWEVER, two sacs does not mean fraternal.

 

My girls shared the same sac but had there own plasentas they called them micro twins they are ferternal but do look alot alike and have alot of the same stuff there birth makes are in the same place and eye and hair are the same but
Mariah is a lbs bigger thats about it.

 

If it makes you feel any better at my 11 week u/s the twins looked like they were in the same sac...the tech really couldn't see the dividing membrane...at my 16 week u/s it was clear that they were actually b/g frat twins...so clearly in two completely separate sacs. They can see things better later on...and also it depends on the quality of their u/s machine... a perinatologist would be the best person to really analyze that and tell you...

Also, just in case they do turn out to be mono-mono twins... According to my mom my id. twin and I shared a sac and a placenta...we were born 28 years ago...with no visits to a perinatologist..no u/s... the doctors didn't even know my mom was having twins... only my parents were convinced that she was having twins... the doctors continually said, 'nope, it's just a big boy...'... she wound up with two little healthy girls born at 38 weeks! We showed those experts!

 

Fraternal twins always have their own sacs (chorionic and amniotic). The sacs grow out of the fertilised egg, so there's just no way they can get to share if they came from different eggs which fraternal twins by definition do.

Identical twins can either have their own individual sacs like fraternal twins, or share the outer sac (chorionic sac) and the placenta (most common), or (rarest) share both the outer and inner sacs (both the chorionic and the amniotic sac). If they share one chorionic sac, they'll also share the placenta. How much identical twins share will depend on when the egg divided into twins - the earlier, the less shared resources.

As everyone has pointed out, the sacs, and especially the amniotic, can be very hard to see on scans - so have patience until next scan

sagertwins, if your girls really shared a sac, they'll definitely be identical and will also have shared a placenta If they're fraternal, they'll have had separate sacs. Identical twins can easily have different weights. Same for you, Twin-kle Twin-kle little stars - if your twins really are monochorionic (=share the chorionic sac), even if they each have their own amniotic sac, they definitely are identical - and they'll share a placenta.

 

When I was first diagnosed with twins at 6 weeks, they couldn't see a membrane separating the 2. At another u/s at almost 8 weeks, they could see the membrane (but it was tough to find- by a perinatologist with a level 2 u/s). The chances of your babies not having a membrane to separate them is very low- only about 5% of twin pregnancies are mono-mono... Congratulations on your twins by the way!!

 

QUOTE(sasja @ May 29 2007, 06:27 AM) [snapback]271262[/snapback]
Fraternal twins always have their own sacs (chorionic and amniotic). The sacs grow out of the fertilised egg, so there's just no way they can get to share if they came from different eggs which fraternal twins by definition do.

Identical twins can either have their own individual sacs like fraternal twins, or share the outer sac (chorionic sac) and the placenta (most common), or (rarest) share both the outer and inner sacs (both the chorionic and the amniotic sac). If they share one chorionic sac, they'll also share the placenta. How much identical twins share will depend on when the egg divided into twins - the earlier, the less shared resources.

As everyone has pointed out, the sacs, and especially the amniotic, can be very hard to see on scans - so have patience until next scan

sagertwins, if your girls really shared a sac, they'll definitely be identical and will also have shared a placenta If they're fraternal, they'll have had separate sacs. Identical twins can easily have different weights. Same for you, Twin-kle Twin-kle little stars - if your twins really are monochorionic (=share the chorionic sac), even if they each have their own amniotic sac, they definitely are identical - and they'll share a placenta.


Sasja,

You are absolutely correct. The chorion is part of the placenta -- fraternal twins CANNOT share this! It is amazing to me how medical professionals can tell their patients misinformation like this. I would think that any doctor, nurse or ultrasound tech should know this simple piece of information. In order to share ANYTHING, there would have to be a SPLIT between the fertilized ovum. Otherwise, there is a completely self-contained fetus with nothing shared, aside from the possibility of having a fused placenta which even then isn't truly shared. And only 1-2% of identical twins share an amniotic sac. It is all dependent upon when the split takes place. Here is an excellent article that is easy to understand:

http://www.twinsmagazine.com/media/images/..._2001to2005.pdf

 

QUOTE(TTTSMiracleMom @ May 29 2007, 01:30 PM) [snapback]271360[/snapback]
Sasja,

You are absolutely correct. The chorion is part of the placenta -- fraternal twins CANNOT share this! It is amazing to me how medical professionals can tell their patients misinformation like this. I would think that any doctor, nurse or ultrasound tech should know this simple piece of information. In order to share ANYTHING, there would have to be a SPLIT between the fertilized ovum. Otherwise, there is a completely self-contained fetus with nothing shared, aside from the possibility of having a fused placenta which even then isn't truly shared. And only 1-2% of identical twins share an amniotic sac. It is all dependent upon when the split takes place. Here is an excellent article that is easy to understand:

http://www.twinsmagazine.com/media/images/..._2001to2005.pdf


Exactly.

 

They definately appear to be in one amniotic sac in those pictures. Mine are in there own amniotic sacs, but at first it appeared they were in the same one. I'm sure that by your next u/s you will be able to tell for sure. At my 15 week u/s we could see a thin membrane separating them, but it is not visible in some of my pictures.

 

My twins were in two sacs inside of one sac. The membrane that divided the two sacs was VERY THIN, and almost difficult to see. But my sonogram pic (at 12 weeks) looked very similar to yours. I think yours are in one outer sac. When I delievered, there was only one placenta - but the doctor's could not tell if at some point there were two and they just fused into one.

The doctor's are assuming that my girls are identical - but could not tell me for sure. They look very much alike, but I can tell them apart. I don't know if it's just because I'm their mom, or what!

My pregnancy was so smooth. I was sick in the beginning, but that is normal. After that, there were so many things to worry about that could happen; but I just focused on being healthy and keeping a positive mindset. I carried my girls full term, and delivered them naturally. They were 6lbs 8oz, and 6lbs 9ozs at birth - and 14 minutes apart.

It is nice to know if the twins are identical or not - but try more to stay focused on the blessing of having two beautiful and healthy babies!! Good luck to you and to all of the expecting moms.

 

QUOTE(TwinsMama11305 @ May 30 2007, 01:33 AM) [snapback]272483[/snapback]
My twins were in two sacs inside of one sac. (...) When I delievered, there was only one placenta - but the doctor's could not tell if at some point there were two and they just fused into one.

The doctor's are assuming that my girls are identical - but could not tell me for sure.

Again, if your girls shared the outer sac, they are identical. Fraternal twins cannot share anything - they come from different eggs that each grow their own sacs and placentas.

Vice versa, if your doctors didn't know for sure if the twins were identical, they cannot have known whether they shared the outer sac.

Identical twins that share the outer sac (chorion) will also share the placenta.

 

QUOTE(sasja @ May 30 2007, 03:40 AM) [snapback]272733[/snapback]
Vice versa, if your doctors didn't know for sure if the twins were identical, they cannot have known whether they shared the outer sac.
Identical twins that share the outer sac (chorion) will also share the placenta.


Correct. I wish medical professionals would become more knowledgeable about this and stop misleading their patients!

 

Thank you for all your replies - they're very helpful. It's reassuring to know that only 1-2% of identical twin pregnancies are monoamniotic. So, most likely, they will each have their own sac.

But, now I have a question, I thought it was possible for twins to be monochorionic/diamniotic but still have separate placentas. And, in this case, they could still be fraternal?

Also, another question - is it true that if there were two complete yolks and yok sacs at an early ultrasound (8 weeks) that they will probably be in their own amniotic sac? maybe even have their own placenta? Is there ANY correlation between yolk sac and placenta/amniotic sac or identical/fraternal?

Thanks again for all the replies - there sure is a wealth of information here. The only thing I'm worried about is monoamniotic, because of the risks, everything else I'm cool with!

Jenny

 

QUOTE(ferfischer @ May 30 2007, 02:43 PM) [snapback]273012[/snapback]
Thank you for all your replies - they're very helpful. It's reassuring to know that only 1-2% of identical twin pregnancies are monoamniotic. So, most likely, they will each have their own sac.

But, now I have a question, I thought it was possible for twins to be monochorionic/diamniotic but still have separate placentas. And, in this case, they could still be fraternal?

Also, another question - is it true that if there were two complete yolks and yok sacs at an early ultrasound (8 weeks) that they will probably be in their own amniotic sac? maybe even have their own placenta? Is there ANY correlation between yolk sac and placenta/amniotic sac or identical/fraternal?

Thanks again for all the replies - there sure is a wealth of information here. The only thing I'm worried about is monoamniotic, because of the risks, everything else I'm cool with!

Jenny


If they have their own placentas then they are dichorionic/diamniotic with is usually fraternal, but some identicals have their own placentas. If they are monochorionic (one placenta) then they are identical.

At 7w my girls had two complete yolk sacs and the u/s tech said that a separate yolk sac was essential for survival. I guess this is what sustains them until the placenta is fully functioning? Anyway, we had two separate yolk sacs and, at that time, were told we had mono/mono twins. We found out later that they are mono/di. Apparently the yolk sacs have nothing to do with the placenta or amniotic sac.

I understand your concerns with them being in the same amniotic sac. I was freaked out when I though mine were. Hopefully you will found out soon that they are not.

Jen

 

Our babies are in two seperate sacs. We just found out last Tuesday that we are having twins and we are SO excited! They will be fraternal, and we don't know their sexes yet.

 

Yesterday I had my first U/S and found out we are having twins, the tech did say she thinks they are in their own seperate sacs. I am so excited I just wanted to share my pics!

http://i114.photobucket.com/albums/n276/jchooker/TwinA.jpg

http://i114.photobucket.com/albums/n276/jchooker/TwinB.jpg

http://i114.photobucket.com/albums/n276/jc...r/TwoBabies.jpg

 

QUOTE(ferfischer @ May 26 2007, 02:48 AM) [snapback]269220[/snapback]
I had my NT scan today, and everything seemed well - but they couldn't really tell if there were two placentas close together or just one - and they couldn't see a membrane between the babies. We're going to have another u/s at 16 weeks to see if we can tell.

In the meantime, what was your pg like if they were in the same sac? Does that automatically mean identical? And, did you have any complications? If so, what happened and what did they do?

Here are some pics to give you an idea...

http://i2.photobucket.com/albums/y2/colofisch/12week2.jpg
http://i2.photobucket.com/albums/y2/colofisch/12week1.jpg

Jenny


Hi,

Ours are in different sacs. It has always been easy to tell for us. Probably the next one will show you more.

 

Our babies are in two separate sacs also.

 

I have mono-di twins. At our first u/s (10weeks) they thought our girls might be mo/mo & I was SO freaked out. At my 13 week u/s they found the dividing membrane. I had so many worries all through the pregnancy, but the babies & I did great. We were monitored pretty closely to make sure the babies were growing fine & we made it to 37 weeks 5 days with a natural delivery!

 

mine were in separate sacs & are fraternal. GOOD LUCK!