From: Rabbi Moshe Sofer
To: Rabbi Gedaliah and Chaim
A woman who nursed her child of unknown paternity for three weeks then weaned him seeks permission to remarry eighteen months after birth. The Chasam Sofer rejects all proposed leniencies — dried-up milk, the child being in another region, threat of apostasy, and a calculated argument that the prohibition will lapse before a new child nurses — holding that the Rabbinic decree cannot be overridden by individual circumstances. He offers only a narrow, non-endorsing concession: if a rabbi has genuinely verified a real danger of apostasy and wishes to combine that concern with the Pnei Yehoshua's precedent on his own authority, the Chasam Sofer will not protest, though he does not agree.
Source: Shu"t Chasam Sofer EH I §35