Hi Mary,
Yes, the 20 week scan is much more detailed than the 12 week one. Coz the baby is so small at 12 weeks, its difficult for them to see much, ohter than how many babies are in there, if there's a heartbeat and a few measurements of the head and legs.
At the 20 week scan they can see much more and are actually looking for some deformaties that they are able to see, if the baby is roughly the correct size, and of course, they can even see the sex of the baby - if it's lying in a clear position! I read it normally takes 20 minutes - compared to the 5 minutes I had at 12 weeks!
I've got an amnio tomorrow so will be able to see baby on the scan screen while they do it - it will almost be worth the pain!! Then my 20 week scan is on 23 October, so I get another little peek before they arrive!
Paula. X