What event marks the beginning of the second stage of labor?

The beginning of the second stage of labor is marked by crowning, which is when the baby's head begins to emerge from the birth canal. This event signifies that the cervix is fully dilated (to 10 centimeters) and the baby is ready to be born. Crowning is a key moment in the birthing process; it indicates that the fetal descent is imminent and that the mother will soon give birth.

While full dilation of the cervix occurs just before crowning and is part of the transition from the first stage of labor to this second stage, crowning itself is the definitive indicator that the second stage has commenced. The first contraction refers to the onset of labor and occurs much earlier in the childbirth process. The delivery of the placenta is associated with the third stage of labor, occurring after the baby has been born. Each of these phases serves a distinct purpose in the overall labor and delivery process, making crowning a critical marker for the transition into the active phase of birthing.