From: Rabbi Moshe Sofer
To: Unknown recipient
When a sage rules a wife's bedikah stain tahor, the Chasam Sofer asks whether her husband may nevertheless adopt a personal stringency and treat her as a niddah, thereby abrogating his onah obligation over her objection. He concludes that the husband may do so, reasoning that Jewish women are presumed at marriage to consent to their husbands' spiritual growth, and just as a wife cannot prevent her husband from becoming a Torah scholar even over her protest, she cannot prevent him from adopting the pious practice of stringency in niddah matters.
Source: Shu"t Chasam Sofer YD §149