Crowning is best defined as which of the following?

Crowning is best defined as the moment when the widest part of the baby's head appears at the vaginal opening during childbirth. This is a significant milestone in the labor process, as it indicates that the baby is very close to being delivered. As the baby descends through the birth canal, the scalp can be seen at the vaginal opening during contractions, and this is commonly referred to as crowning.

Understanding this term is crucial for recognizing the progress of labor and the impending arrival of the baby. The other definitions relate to different aspects of the childbirth process, such as the bulging of the head or the dilation of the cervix, but they do not capture the specific moment of crowning which is unique in that it signifies the baby's head becoming visible.