Which findings indicate that placental detachment has occurred after delivery?

The correct answer indicates that all the provided findings can signify placental detachment after delivery.

Lengthening of the umbilical cord occurs as the placenta separates from the uterine wall; as the cord pulls away from the placenta, it appears longer because the placenta begins to descend into the vagina. This observation is one of the initial signs that the placenta is moving away from the uterus.

The sudden gush of dark blood from the vagina is another classic indicator of placental detachment. This blood typically appears as the placenta separates from the uterine wall and is no longer contained within the uterus, allowing the blood to exit the body. The dark color indicates that it is older blood, which can be a result of the detachment process.

Lastly, the appearance of fetal membranes at the introitus is a definitive sign that the placenta has detached. As the membranes descend into the birth canal, they signal that the placenta is ready to be expelled.

Considering all these criteria, it's evident that each finding contributes to the overall understanding that placental detachment has occurred. Thus, the inclusion of all the findings as indicators supports the conclusion that they collectively signal this critical step in the postpartum process.