Shoulder dystocia and congenital plexus palsy have become a paradigm in medical liability, although there is great uncertainty regarding the pathogenetic factors involved. In this article, clinical evidence and theoretical considerations are presented to extend the current commonly adopted view that neonatal plexus injuries are the result of incompetent medical manoeuvres following anterior shoulder blockage at the symphysis. Without any medical intervention, the posterior shoulder could experience the same arrest by the promontory when attempting to pass the pelvic inlet, explaining connatal paralysis without medical intervention. This sacral shoulder dystocia takes place at a much higher level than symphyseal shoulder dystocia and is therefore hardly recognisable as such clinically; thus, it cannot lead to faulty manipulations. Furthermore, available data show the ability of endogenous birth forces to cause such injuries. The possibility of these and other pathogenetic mechanisms should be considered in legal practice to avoid conclusions with little justification.