The birth canal, the passage through which a baby is born! Part of the birth canal is the \”osseous birth canal\” composed of bones, and the other part is the \”soft birth canal\” composed of muscles and ligaments, which refers to the part from the cervix below the uterus to the vaginal outlet. The uterine opening is closed before labor begins. As labor progresses, the connections between ligaments and bones loosen and soften. Once labor begins, the birth canal opens enough to allow the baby to pass. size. A good birth canal condition is that the bony birth canal is not narrow, the soft birth canal is normal, and the stretch force is good. The fetus rotates in the birth canal