Hello. Girls, could you please tell me how to conjugate external if it…

Hello. Girls, could you please tell me how to conjugate external if it's not in the norm during childbirth? I need a size 20 for my vagina but I am a 17. They say that Cesarean section is better than natural birth. How was it for you? As I understand, the vagina is measured with several measurements and if even one of them doesn't fit the norm, then it's considered a narrow pelvis.