My wife and I were at the mall over the weekend and we started talking about how some women find men more attractive if they are holding a young child. I guess a child could be considered an icebreaker allowing the women to come up and begin talking. This could work for a women too. A terrible way to look at it but a child could be considered an accessory by some people. Here is how I see it.

Man holding a child
Pros from a woman's view:
A man holding a baby may mean that he is caring and takes responsibility for his actions. Men who publicly play with their child may be considered even more attractive as women seem to have a belief that men don't want to be fathers. A father who is playing with his child does not care what others think and is confident in his fathering.

Cons from a woman's view:
A child being taken care of by a man may be seen as a taken man. While this may not stop some women from continuing, many women don't want to step over that line. As much as they are attracted to an involved father, there is always a boundary.

Woman holding a child
Pros from a mans view:
One of the things that doctors will always tell you is that men look for women who are fertile. A mother holding a child would normally mean that she is in fact fertile. Subconsciously, this is what we want.

Cons from a mans view:
There are many men who dislike children so much that regardless of how beautiful the women is, the child will keep him away. Unfortunately, these are commonly the men who leave their pregnant girlfriend/wife soon after hearing.

The bottom line is that if you don't want a good looking girl to come up to your husband, don't leave his side. It is bound to happen otherwise.
Care to add anything?