Final answer:
A prolonged latent phase in multiparas is defined as a latent phase lasting more than 20 hours, and this phase typically shortens with each subsequent labor.
Step-by-step explanation:
In the context of labor and delivery in multiparas (women who have given birth more than once), a prolonged latent phase is typically defined as one that lasts more than 20 hours. The latent phase is the initial stage of labor, where contractions begin and the cervix starts to thin and dilate. It is known that the length of this phase may take minutes, hours, or days, and notably, it tends to be shorter in subsequent labors. According to this definition, the accurate option for a prolonged latent phase in a multipara would be c) More than 20 hours.