I could think of it as more of a certificate you get when you graduate from a course where attendance is the only criteria for getting the certificate, unless there are other mitigating circumstances.
So, for 99% of people, they go on a few parenting classes, learn how to hold, wash, feed a baby, learn abit about discipline etc etc and then get their certificate. But for 1% of people who have a violent criminal record, rapist, pedophile, convicted drug user or other such criteria (such definitions to be defined using the normal criminal statutes we already have to define "bad people") they would have to pass some additional test to get their certificate. Except for pedophiles who should be banned for life. That would be simple, fair and hit the objective of preventing only those really nasty pieces of work from having kids.
Oh and as for teenage pregnancies etc etc - compulsory attendance at the course as soon as you know you are pregnant or give birth, whichever is earlier. No "penalties".