Which sign is definitive for imminent delivery of a baby?

Crowning is indeed the definitive sign of imminent delivery because it indicates that the fetal head has descended into the birth canal and is visible at the vaginal opening. This signifies that the baby is very close to being born, as crowning typically occurs during the second stage of labor when the cervix is fully dilated. When the crown of the baby's head appears, it is a clear indication that delivery is not only imminent but imminent within minutes.

While the urge to defecate can suggest that the baby is descending and pushing against the rectum, it is not as definitive as crowning, as it can occur at various stages of labor without indicating immediate delivery. Lengthy contractions and contractions occurring less than three minutes apart can indicate that labor is progressing and the delivery might be near; however, they do not provide the same level of certainty about the baby’s imminent birth as crowning does. Thus, crowning is the most unmistakable sign that labor has progressed to the point where the delivery is about to occur.