Thank goodness we can now do painless (until afterwards) C-sections. Symphysiotomy was, in some cases of obstructed birth, the only way to save the life of the woman and sometimes the fetus, although crushing the fetal skull might also be necessary. It can still be done in places where a C-section isn't possible, and it requires less medical skill. One would use anesthesia or whatever was available to diminish the pain.
Fun fact in case you're not cringing enough: the symphysis is the cartilage joining the pelvic bones right up under the clitoris. So, nerve city, pretty much.