Advice needed. Playpens

We are having our first child in June and My inlaws offered to help us with baby sitting but during a conversation, my mil said something about putting the child in a play pen. I'm not very familiar with these but I googled them and I don't like what I'm reading. I want to tell my mil that there is no way in hell my daughter is to be put in a play pen but this being my first and her having raised kids, I'm not sure if I should. Are playpens safe or should I be worried?