Second shadow on ultrasound??

[Pocket]

Hi!

So I had an early scan to determine due date (PCOS). There was one very obvious sac and baby BUT! there was a second shadowthing. Same size as the embryo. Doc couldn't get around the first to see what the shadow was. She said there may be two but it'd be more obvious at the next 10 week scan. Said she couldn't positively identify it as multiples yet but that there was a good chance.

Ok ladies, what could it be other than twins? Anyone have this happen? I'm not worried (much) because the one she could see measured ok and had a heartbeat. But what was the shadow? Weird! Only one visible yolk sac. Identical twins? I was too stunned to think of questions to ask while I was there. Shouldn't she have been able to get two heartbeats?

 

[hellojello25]

I believe the other thing it could be is an embryo that failed to properly develop. As in, it would have been a twin, but something went wrong with the development and it's being reabsorbed. At 10 weeks, if there's nothing there then that's probably what it was. If the shadow develops into another sac + fetus, then you have twins. Fraternal twins though, identical share a sac and both would already be visible I believe.

Edit: I went back and reread your post. The shadow was inside the sac? That could be an identical twin then. They're very very small at that age and since they share a sac and an artery (?) they have to stay close to each other, but at 10 weeks they should be able to tell for sure because the fetuses will be more developed.

 

[BunnyN]

I would think there might be other possibilities like a small bleed or something? How many weeks are you?
Early on they are so tiny it's not that uncommon for a twin to be missed altogether.

 

[Dill]

I had a friend who had twins and despite regular ultrasounds and fetal doppler checks, the doctors didn't realize there were two in there until somewhere around 20-24 weeks (they're 4 years old now, so I don't remember specifically anymore). One was hiding right next to the other and they had pretty well synchronized heartbeats, so the second twin went totally unnoticed.

So it's certainly possible that there's another one in there!