After 10 months into our relationship, my girlfriend is just telling that she had a baby before she met me. I'm confused.

Should I keep dating her?

Why did she wait so long, and where is the baby? You have asked her all these questions when she told you right? If NOT, why NOT?

I will agree, where is the baby? After 10 months, I would have assumed you would have know.

But perhaps, this is a secret, (baby adopted or living with family)

In and of itself, she may have felt her past, if it does not effect currrent relationship did not need to be discussed

From a female...

She wanted to get to know you first. She didn't want men coming and going out of her baby's life. As a woman I see this as a very responsible action on her part.

You really didn't give us enough information to go on.