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:www.naturallyparentingtwins.com
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!)http://www.uptodate.com/home/content...=labordel/5122