[If a woman] was pregnant, and they said to her: “What is the nature of this fetus?” [and she replied: “He was fathered] by so-and-so, and he is a Kohen” —- Rabban Gamliel and R’ Eliezer say: She is believed. R’ Yehoshua [however] says: She is not be-lieved. Rather, it is presumed that she is pregnant from a Nesinite or a mamzer, until she proves her claim.