How many weeks can you tell via ultrasound...

...if your twins share one sac or are are in seperate sacs? I went in on Wednesday and found out that we are expecting twins! Right now it looks like they share a sac but the tech mentioned that we're right around the cut off mark where they may still split or we just cannot see the tiny membrane seperating them.

So, how far along were you when you KNEW they were in the same sac or seperate? Has anybody experienced this and then later had them seperate?

Thanks in advance, I'm new to this

 

I had fraternal twins in two different pregnancies identified by ultrasound at 8 weeks. We had very clear distinct shots of two sacs and a separating membrane.

 

I've also had two pregnancies that were di-di (separate placenta, separate sac) very visible on u/s at 6.2 weeks each time (first one we had a vanishing twin and it resulted in a singleton pregnancy).

That said, you seem to be asking about mono-mono or mono-di twins. There was a thread recently in which someone asked about when they are able to see the membrane and got lots of good responses (hers initially didn't look like they had a membrane but they eventually were able to see the membrane on ultrasound making her twins mono-di--one placenta, two sacs). Mono-mono is very rare (less than 1% of twin pregnancies).

http://www.twinstuff.com/forum/index.php?/topic/174456-hi-im-new-terrified/

Hope that helps!

 

We found out at 6 1/2 weeks I believe. We saw two sacs & two heartbeats. How far along are you?

 

I posted in the other thread, in any case. I found out at 8 weeks we were having twins, the tech couldn't see the membrane but at 16 weeks they found the membrane - I had a mono-di pregnancy.

 

We found out at 9 weeks we were having twins and they could see the membrane at that time (we had mono-di). They said the earlier ultrasounds are the most important in looking for the membrane and they said it actually gets harder as the babies continue to grow. Best of luck!

 

To answer the question, I'm 8 weeks 6 days now. My ultrasound was at 8 weeks 1 day.

 

I found out I was having twins at 8 weeks - we did not see a membrane until 21 or so weeks ... mine were mono-di. Good luck!

 

[To update, I had another ultrasound on the 27th and found out that they found a membrane. They also confirmed only 1 placenta. I'm so relieved!!! :woohoo:

 

Great news! Now it's time to see a high risk doc and push for weekly ultrasounds to monitor for twin to twin transfusion syndrome. It is rare, but does happen.. There is treatment so it's important to catch it. Best of luck (from a mommy of twin to twin survivors!)

 

I don't go back to my doctor until 16 weeks (I'm 13 now). Then he's referring me to a specialist at 20 weeks. Should I try to go in for an ultrasound sooner?

 

I would try to have the u/s at 16 weeks and then make the appointment for the specialist at 20 weeks, after that you will probably be going every fortnight if not more.