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what exactly does "sep. by thin membrane" mean

post #1 of 7
Thread Starter 

Well I got the shock of a lifetime on Thursday at my 20 week scan when the US tech said "you know you've got 2 in there, right?" I did not. So bye-bye homebirth and hello to tons of questions!

The tech said that the twins share a placenta and are separated by a thin membrane. So, question is: is this considered diamniotic or monoamniotic? Is it one sac with a thin membrane, or two distinct sacs? And is the membrane pretty stable, or could it break or go away... I know that sounds silly, but I want to know if I need to think about the risks that come along with mono/mono twins.

Many thanks in advance, and I look forward to getting to know you all!

post #2 of 7
Congrats on your pregnancy! I do have to ask why you cannot have a homebirth with twins. I've had 2 homebirths with my singletons and expect to have my twins at home, as well.

As for your question, I believe that they would still be considered monochorionic/diamnitioc (identical twins!!).

I found this website/document and it's full of very informative/interesting info!! Hope it helps! They even have ultrasound pictures at the very end showing what the differences in the chorionic/diamiotic, etc means!

post #3 of 7
Thread Starter 
Thank you!

I haven't completely ruled out homebirth, but am not completely comfortable with it for myself for twins. First, in NJ, it is illegal which means if I have a transfer Ill probably get treated like %$#@ at the hospital. b And, I may have to deal with DYFS. And, pay out of pocket. It is not completely out of my realm of possibility. I am talking with a hbmw today and also will begin calling hospital mws- compare all options and make the decision that feels best.

what is your estimated date of delivery? im excited for you to be birthing them at home!
post #4 of 7
Hi! No time to write much. I homebirthed my twins and it was a great experience. Mine we also "discovered" at the 20 week u/s. Twin shock!

I decided on a HB late in the game, because twin hospital birth is so medicalized. That's something you'll find out. I really didn't think it was very different at home, so long as you have a great, experienced midwife. And there are some. Mine came from central PA, with lots of work with Amish women. I was her 43rd twin HB.

But you can read all about twin HB here, and on another good site:


One thought - my twins are identical (DNA tested) and had one placenta. But I'm 99% sure they were di-di, and that the placentas fused. That is a very real possibility for you. Lots of placentas fuse. Next u/s, as soon as you can, have the tech look at where the membrane meets the placenta. Is it a "T" or a delta? T is more likely mono-di, delta is more likely di-di with a fused placenta. I say check this as soon as you can, because the later it gets, the harder it is to tell the difference. You may already be too far along to know for sure.

Buuuuttttt, if there's one placenta and the membrane is indeed thin at 20 weeks, your docs will treat your pregnancy as mono-di. Which could be right. There's different thinking on mono-di pregnancies. Some people think as long as there are 2 amniotic sacs, a healthy pregnancy and no TTTS, you should be good for a full term natural delivery. I lean that way. But I can't ignore research that suggests there are added risks for mono-di pregnancies, even beyond TTTS. Sorry, I'm not trying to scare you, just trying not to be cavalier and give you the best advice I can. You're likely to be pressured to deliver early. Early delivery carries it's own risks. These are ones you'll have to research and weight.

Have a thick skin and an open, inquiring mind. The next few months will be wild. Read a lot, and take what you read and your doctor's advice with a grain of salt. Take care of yourself - lots of water and protein. Rest and activity as your body tells you.

IMO, especially with the possibility of mono-di pregnancy, you will need a good OB or peri, and should get lots of care. Ask around, especially at your local twin club for the best docs / hospitals. But that doesn't mean you can't have a HB, assuming all else goes well and you still want one. I did parallel care at the end, which gave me the confidence in my health and the health of my twins to birth them naturally.

Here's my current favorite article (which is of the camp that di-amniotic is all you need!)


Best wishes!
post #5 of 7
Congratulations! I also found out at the 20 week u/s. Talk about floored! I think your questions have been answered. We were never able to find out if ours were identical because they couldn't see the alpha or T that late in the game. They think I was just like you, large or fused placenta, thin membrane.
post #6 of 7
Home birth is illegal in Illinois, as well. But, the doctors here have already stated healthy pregnancy or not, they will not "naturally deliver" twins because there are too many risks. So, if I go the hospital route, it will be a mandatory c-section at around 36 weeks. Not cool with me. I don't like that at 11 weeks, they are already preparing me for a mandatory c-section. I feel better "taking my chances" with a homebirth.

I hope you find a way to birth the twins the way you want to!!!
post #7 of 7
You need to get a more detailed u/s to find out exactly what that means. Sounds like monochorionic/diamniotic twins. In that case, you're at risk for TTTS, as Gena mentioned.

Personally I wouldn't feel comfortable homebirthing with monochorionic twins just because mine had TTTS and that is something that has to be watched very carefully.
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