My first problem with this is, how do you enforce it? Who decides who passes the test or not? Do you sterilise everyone until they pass the test? Do you force abortions on people who wouldn't meet the criteria? I don't see a way to do it that isn't a gross violation of individual rights, and that wouldn't potentially force women who accidentally became pregnant to eschew maternity care just in case they weren't judged worthy.
My second issue is that a lot of people change once they have children. Just because someone is an immature prat before they have a child doesn't mean they won't grow up once they do. It's not guaranteed by any means, but it does happen.