It was the way of the sages to speak of meetings and discussions between the rabbis and members of the imperial Roman family of their era. The sages considered the contents of the discussion as greatly important and learned from them laws and practical customs. For example, they related that a daughter of a Roman caesar, Justinia, asked Rabbi Judah the Nasi (editor of the Mishnah) two questions. 1. At what age may a girl marry? 2: At what age can a girl become pregnant?
Rabbi Judah the Nasi answered the first question, saying that a girl may wed from the age of three. To the second question he answered that a girl can become pregnant from the age of 12. Justinia, daughter of the caesar, responded that she was married at age six and had a child at age seven and so is testament to the error of his answer. So ends the story of the encounter. From the discussion between the caesar’s daughter and Rabbi Judah the Nasi, one may conclude that a six year old can become pregnant, and so the sages of the Talmud ask: how is it possible that she became pregnant at age six? The sages, after all, had determined that a woman can only become pregnant from the age of 11. They were answered with two possibilities for reconciling the words of the sages with those of Justinia, daughter of the caesar.
1. She is a gentile, and it is possible that they become pregnant younger, while still little girls, even at the age of six. This is unlike Jewish girls, who become pregnant only from the age of 11. (In the words of the Talmud, “Their flesh is as the flesh of asses.”)
2. Justinia, daughter of the caesar, lied as is the habit of gentiles.
(Babylonian Talmud, Tractate Niddah 45a)