What defines a revealed (marginal) abruption?

A revealed (marginal) abruption is characterized by the bleeding that emerges from the edge of the placenta, making this option the correct choice. This type of abruption occurs when the placenta partially separates from the uterine wall, and as a result, some of the blood is able to flow out of the uterus and into the vagina, which can be a crucial indicator for diagnosis and management of the condition.

In this context, the other choices do not accurately describe the characteristics of a revealed abruption. The first option, referring to bleeding at the center of the placenta, describes a different presentation of placental abruption, likely leading to more severe outcomes. The second option implies that the bleeding is confined entirely within the uterus, which is typically associated with a concealed (or internal) abruption rather than a revealed one. Lastly, the option that states no bleeding is present is not relevant to a diagnosis of any type of placental abruption since bleeding is one of the key signs that suggest separation of the placenta.