From: Rabbi Moshe Sofer
To: Rabbi Naftali
A bride who had premarital relations with her groom under formal engagement (tena'im) received a kesubas besulah of 200 zuz. The Chasam Sofer rules the kesubah stands in full, distinguishing this case from the Dagul MeRevavah's ruling that a seduced bogeres receives only 100 zuz: since the woman consented to premarital relations in reliance on the binding engagement and expectation of a full kesubas besulah, her consent cannot be deemed an unconditional waiver, and in any event the husband already wrote 200 which the court cannot reduce.
Source: Shu"t Chasam Sofer EH I §125