a couple of questions....about early pregnancy and twins...

[biggulp]

Firstly, had a scan at 6 weeks (viability). i had had a feeling it was twins and on the scan there was one fetus with heart beat and measuring right for dates, and an empty looking sac. was told it was vanishing twin syndrome but that the remaining singleton looked good.

now. that's all good, but i am feeling incredibly rough, and massive. is there a chance that although nothing could be seen in second sac it will still be there and i'm still carrying twins?

well , if you were having fraternal (non identical) twins then that second egg could have been fertilised a lot later than the original one - hence it not showing on the scan - although i would have thought maybe a sonographer would have thought of that - you never know. If they are id twins then they would have been fertilised at the same time. Non id twins could be the result of two eggs either ovulating together but being fertilised separtelty. if i was you i would ask for a second scan - fake a symptom if you have too - at least then you will know. I have ID twins btw.

i can't find anything online to suggest that twins can develop at different rates leading to mistaken diagnosis of vanishing twin syndrome.

It's very rare, two babies of different gestation but does happen.