I am 13 weeks pregnant with twins and found out at 11 weeks.
The doctors are saying they are in one sac but wont give me a definite answer about them being identical.
What does it mean that they are in the same sac? Is it possible for a membrane to just show up at any time?
All women have an inner sac (the amnion) and an outer sac (the chorion). Fraternal twins always each have their own amnions and chorions. Identical twins may each have their own amnions and chorions, they may share a chorion, or they may share both an amnion and chorion. It sounds like they think the babies share either a chorion or possibly both an amnion and chorion, but are not sure yet.
The way to really tell if they are identical (short of an expensive DNA test) is to have the placenta and membranes checked under a microscope after the babies are born.
There are lots of good web sites that talk about what you need to do to have a good pregnancy and a safe vaginal birth of your children, and they also provide lots of tips for moms of multiples.
Good luck to you!
-- Cynthia, CNM. PhD