Date: Erev Shabbos before Yom Tov (written in Frankfurt am Main)
From: Rabbi Moshe Sofer
To: Rabbi Wolf (Volf)
The Chasam Sofer rules that non-Jewish doctors' medical opinions are halachically worthless, and that their prescriptions actually worsen the situation by confirming the blood originates from the uterine source. He endorses the bedikah method of the Emunas Shmuel and insists that even when leniencies apply, the husband must withdraw with a non-erect member as a precaution. He firmly rejects the student's argument that a woman with an established veses need not worry about irregular sightings, affirming that every woman must be concerned about even a single non-established sighting.
Source: Shu"t Chasam Sofer YD §160