A:If the lady has a full ten days of menstruation then it will be permissible for her to have a sexual relation with her husband before bathing.
If her usual menstruation is less then ten days, e.g. five days, six days, etc. then in this case she is not allowed to have a sexual relation until she has a bath. In this case a sexual relation will be permissible if one Salaah time passes without her bathing. After one Salaah time passes and the Salaah becomes Qadhaa on her then it will be permissible. She should remember that staying in that condition without bathing and missing a Salaah is a major sin.
Allah Ta’aala knows best.
Moulana Yusuf Laher