Please honour your body during menstruation. Over time, you will get to know your body and practice but, for some women, classes are to be avoided during heavy days. For all women during any stage of menstruation, it is recommended that you remain gentle during any pose or breathing exercise that may involve movements in the lower abdomen.
It is also common to find difficulty balancing during this time of the month. Any pose where the pelvis is upside down (e.g., Legs-Up-The-Wall Pose, Viparita Karani) is not advisable during this time.