Talk to Gynecologist on Normal Vs C Sec

I am 38 weeks pregnant Alhamdulillah and during my last checkup my doctor said that the pelvic bone is tight due to which baby head is not getting engaged. Therefore I should go for a c sec. Is the pelvic bone theory a myth and does it expand when having pains or should I opt for an early operation? My cervical length is 40mm Waiting for a positive response