I think the OP is asking if it is ok to breed a 10 yr old maiden...
Generally the older a mare gets, the more difficult it is for her to catch the first time, but other than that there isn't usually any more problems with the pregnancy than with a younger maiden.
I've been told that 12 is a perfect age for breeding a maiden and that people have bred 17 and 18 year olds for the first time, so no, 10 is not too old. Other than that, there's no real risks attached to a horse in her teens having a first foal-she just might not be as likely to catch, as ilovesonya said.
Let me just add that breeding is a huge responsibility. It takes a lot of time, money, and planning- and any pregnancy can be risky. Before you breed, look at all of your options. What do you want the foal for? Would it be a better idea to buy a foal than to risk your own mare? Are you willing to do all of the training? Are you capable? What kind of market would there be if you needed to sell it?
Don't jump into things head-first. Evaluate and plan.
Please, lets not start this into a "Don't breed" conversation.
OP, I bred my maiden mare at 16 years of age. Probably not the best idea in the world, but not horrid. She foaled with out a hitch in the least, wonderful mother except she didn't want to wean! Even after I kept the foal away for a few months, she would let him suckle.
So no, 10 years of age is fine, though like one person said, it could come with a bit of complications with a maiden mare.