While preparing a class on Miriam last week, I came across essays (here and here) which show that Josephus and Pseudo-Philo, in the first century CE, presented a diminished version of the midrashic tradition regarding Miriam.
In rabbinic tradition - which Josephus and Pseudo-Philo demonstrate that they knew, even as they report it in an altered form - Amram and Yocheved, parents of Miriam and Aharon, separate from each other when Pharaoh decrees the death of Jewish baby boys. Miriam reports a prophetic vision that her parents will produce a son who will rescue the Jews, and she convinces them to return to each other. Then, when that baby (Moshe) is put into a box in the river, Miriam stands guard over him. [See Exodus 2 and Talmud Megilah 14a.]
In Josephus' Antiquities of the Jews II 9:3-4, per the Whiston translation available here, there is no separation of husbands and wives. Amram has a vision that his son will rescue the Jews from Egypt, and Miriam goes to the water to watch over Moshe only because her mother has told her to do so.
In Pseudo-Philo's Biblical Antiquities of Philo 9, per the James translation available here, the husbands and wives separate, but Amram is the one to insist that Jews continue to have children. Miriam does then have a vision regarding Moshe, but she does not watch over Moshe on the river at all.
What is this evisceration of Miriam's role about? Is it simply misogyny? Or an attempt to conceal from the Romans the possibility of Jewish insurrection, as represented by a fearless Miriam? Or something else entirely?