Several times before the ward round came round and the Obstetrician was suspiscious and double checked at which point the woman was prepped and whisked off for an emergency caesarean. This was when I was a student and the midwife I was working with was happy about me performing the vaginal examinations. I have learned to be more thorough in my observation and examinations now. It is very hard as a student to forgive yourself errors but it is important to do so. It is one of the aspects of how we learn.
Women are different, labours are different, and what is right for one is all wrong for another.
It is usually not risky to let labour take its course rather than acting on a suspicion or fear that it won't work. This article cites increases of 1cm in transverse and 2 cms to the a-p diameter of the outlet, when the mother is in squatting position Other references are found in the article. They combed the Canadian archives for stories about midwives and birth from the pioneer days. For those who were not too proud, there was the possibility of learning from the midwives. Often, a midwife would be willing to accept the status of assistant, while actually functioning as a teacher.