Before you can become a plumber or a carpenter you have to undertake years of technical training, work under close and exacting supervision, sit for exams, and earn your ticket. No one gets to be a doctor, lawyer or accountant unless they first qualify for university, then study day and night for years, sit regular and sometimes arduous examinations, and pass with flying colours. But to become a parent, all you have to do is find a partner, cross your fingers, and hope for the best.