Chainsaws Were Originally Designed for Surgery
You don't need to see any horror films to understand that the concept of mingling flesh with a chainsaw is unpleasant. They are ruthlessly effective tools that quickly chop down trees, thus it stands to reason that they would cause catastrophic harm to living tissue. Despite this, there was a time when chainsaws were used as medical equipment.
The first chainsaw was invented by two Scottish surgeons in the 18th century. One of the early purposes was to remove damaged bone, and while painful, that does seem plausible. Symphysiotomy was the other aim that was envisioned. To aid in birthing, the pelvic region has been widened in such way.
These early chainsaws were used to cut the pelvis apart when caesarean sections were not an option. The premise was essentially the same, even if the instruments were hand-cranked and much smaller than those a lumberjack might use. A small, knife-sized spinning saw was used to remove cartilage from the pelvic region, enlarging the area by a few centimetres to facilitate birthing.