It depends which country I'm living in!
In England, always a bunch of flowers and a bottle of wine.
In Belgium, a box of chocolates.
In Germany, it varied depending on whose house we were going to and how well we knew them, but usually a bunch of flowers with something else. A little present for any children in the house was the norm there.
In Singapore, nothing, though the occasional bottle of Champagne always went down well!
My parents were German, Verity, and they always brought something for the children -I have not heard of people doing this since, until you mention it now -must have been a German custom!
You just did not go to anyones house who had children, without taking them a present.
We were a bit surprised the first time someone came to dinner and brought a present for our son but soon learnt it was the done thing in Germany. A rather sweet custom I think, as usually dinner hosts have plenty of wine already and struggle to cope with finding vases for bouquets when they are also hanging up coats and trying to prepare a meal! Handling a present is much simpler :)