During which stage of labor does the cervix dilate?

During the dilation stage of labor, the cervix undergoes the process of widening or opening in preparation for childbirth. This stage is critical because it allows for the baby to move through the birth canal. The dilation of the cervix is measured in centimeters, ranging from 0 to 10. A fully dilated cervix at 10 centimeters indicates that the mother's body is ready for the expulsion stage of labor, where the baby is delivered.

Other stages of labor, such as expulsion and placental, involve different processes. The expulsion stage focuses on the delivery of the baby, and the placental stage involves the delivery of the placenta following birth. The transition stage is part of the dilation process, occurring just before the expulsion phase and characterized by further cervical dilation and significant contractions, but it is not the stage where dilation primarily occurs. Therefore, the dilation stage is specifically defined by the cervix opening, making it the correct answer.