From: Rabbi Moshe Sofer
To: Rabbi Meshulam
A first-time mother found blood after marital relations six times, always on the night of immersion, with fright from cold mikvah water causing trembling. The Chasam Sofer acknowledges the Rashba's strict position but identifies four cumulative mitigating factors — years of normal relations, a regular veses falling outside these episodes, physical disruption from first birth, and fright-induced loosening of the womb — and permits relations on the second night after immersion in warm water, with a specific procedure for the first test intercourse.
Source: Shu"t Chasam Sofer YD §183