One sac that is measuring a week and a day behind the other. I am 6w6d. My RE said she is concerned because of the size but that the heartbeat of 121 is a good sign. Baby A's hb is 128 and he/she is measuring right at 6w6d. 
I don't know how to feel at this point. Anyone have any personal experience or insight? It's amazing to me how much I already love these little ones growing inside me...I don't want to lose either one :
Re: Two babies, two heartbeats, but...
Congrats on your babies!
I wouldn't worry about the measurement at this point. My RE measured our sac yesterday at 6 weeks 6 days even though I am 6 weeks 2 days. I was talking about it with a friend later and she mentioned that even a millimeter difference on the measurement probably changes things at this early stage.
As long as they both have strong heartbeats then I would say you are fine!
"I prayed for this child and the Lord has granted what I asked of him." ~1 Samuel 1:27
"Whatever it takes, we walk together." ~Pittsburgh Penguins
My IF-turned-baby blog
IVF #1 = BFN
FET #1 = BFN
FET #2 = BFN
IVF #2 = BFP, b/g twins lost at 20w due to partial abruption/PPROM
IVF #3 = c/p 5w2d
Long-shot Clomid/Prednisone cycle before next IVF = BFP, our beautiful, healthy girl born 6/26/13!
~~
TTC again March 2014
FET #3 - May/June 2014 - all embryos arrested before xfer - back to the drawing board...
IVF #4 - July/August 2014
dx MFI 10/10
IVF #1 10/11-11/11 BFN
IVF #2 1/12 BFP! 1st u/s It's twins!
Congrats!! Your all 3 in my thoughts and prayers.
Blythe Elizabeth is here March 27,2012
I am hoping for all the best for you. I was in a very familiar situation. My "Runt's" sac was measuring a week behind his sibling and he was a little smaller. He had a strong HB a couple weeks ago (130's), but was still measuring behind his sibling a little (which they say is normal for twins...). We went for our 10 week u/s this morning and found that he had no HB and had stopped growing after our last u/s. Our Dr had mentioned to us that he was smaller and that there was some concern, which I appreciate. I would have hated to have been completely unaware there was some concern walking into our appointment this morning.
I am hoping the absolute opposite for you. I just didn't really believe it could happen to us, after seeing his little HB 3 times, I thought we were in the clear...but we are a little devastated now.
Best wishes on your pregnancy. I am hoping that your twins grow up big and strong.