Menstrual Periods

Bukhari :: Book 1 :: Volume 6 :: Hadith 317

Narrated 'Aisha:

Fatima bint Abi Hubaish used to have bleeding in between the periods, so she asked the Prophet about it . He replied, "The bleeding is from a blood vessel and not the menses. So give up the prayers when the (real) menses begin and when it has finished, take a bath and start praying."