3 Answers

PG stands for Parental Guidance.  It's up to the parent to decide if the contents of the movie are things (s)he wants the child to watch unchaperoned. 
If it's a PG-13, I would veto that without further discussion.
Why don't you just make some time to preview the movie, or watch it with the child. 

I wouldn't suggest it. In Sweden and in Germany many movies like American Pie are allowed for children to watch. I have seen the movies, in my eyes. Not in my watch that my "10" year old would watch. I'd forbid it!

You have choice to do that, when I was 10 years old. I watched the Grudge and that was PG :(
It gave me nightmares and I couldn't ask it to stop.

P G means Parental Guidance. That means you should at least clue him in on some of the subject matter before he/ she sees it.  Read the reviews,or watch it before you let your kid watch it. Or, talk to some other mothers who have seen the movie. You are your child's first adn greatest teacher   :-)