There is a large number of cesareans being performed with the diagnosis being CPD (cephalopelvic disproportion). This is when the baby's head is too large to pass through the mother's pelvis.
And in most cases it is a completely bogus diagnosis. Sometimes this diagnosis is made without the woman even laboring! In the absence of a pelvic deformity there is no way to know whether a woman can birth vaginally until she has labored and pushed in positions of her choosing with a baby that is presenting correctly.
The diagnosis is made during labor sometimes because of a care providers failure to wait or a malpositioned baby.
This video shows women who had their first cesareans for "CPD" and then went on to birth vaginally, often giving birth to babies that were larger than the one that was supposedly too large to pass through their pelvis.
Very rarely does a woman's body grow a baby too large for her to birth.