Abu Sa‘īd al-Khudri (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "Among the most wicked people in the sight of Allah on the Day of Judgment is the man who has sexual intercourse with a woman and then divulges her secret."
The noble Prophet (may Allah's peace and blessings be upon him) informed us that among the most wicked people in the sight of Allah on the Day of Judgment is someone who commits a betrayal by divulging the secrets of what goes on between him and his wife; things that no one else would know except the husband and wife. This Hadīth declares the unlawfulness of disclosing what goes on between a man and his wife in relation to sexual intercourse, describing the details, and revealing what the woman says or does. As for just mentioning sexual intercourse, if there is no benefit or need for it, it will be disliked, because it goes against the sense of honor. The Prophet (may Allah's peace and blessings be upon him) said: "Whoever believes in Allah and the Last Day let him say good or remain silent." However, if there is a need to mention it or a benefit in talking about it, such as criticizing a man for shunning his wife or a wife claiming that her husband is impotent, in these cases it will not be disliked to mention it due to the benefit it entails, which has been proven by the Sunnah.