The following extract comes from the book "Yogic Management of Common Diseases" by Dr Swami Karmananda;
The monthly hormonal cycle of menstruation serves as a constant backdrop for the mental and emotional state of every woman, as well as an important factor in her overall state of health.
From a spiritual point of view, the days around the menstrual period are very powerful and auspicious for a woman to practice meditation and japa yoga (repetition of mantra).
The period commencing three days before the onset and continuing for five days of menstrual bleeding and the first five days of the new cycle is a time when a woman gains a heightened level of awareness naturally, by virtue of the altering hormonal balance.
This is a time when her natural insight and intuition becomes very prominent, and it is a most powerful time for psychic awakening.
During this period sense perceptions, psychic receptivity and intuition spontaneously sharpen; for example, a woman may become very much more aware of smells, sounds, textures and tastes. She may feel unusual repulsions or attractions which really reflect her altered state of awareness.
Many women become frightened because of unusual perceptions and experiences and may mistake them for hallucinations or symptoms of sickness because they fail to understand what is actually happening.
Much of the pain and suffering of menstruation is due to fear and tension.
When yoga is used to re-balance the disordered muscular and hormonal imbalances which distort menstruation, and fears and tensions are relaxed, the process will be seen in a different light - as a blessing in disguise.
It is a period in which access to a higher level of awareness is temporarily available and this should be met with confidence.
Yoga and meditation are the means of transforming the menstrual period from a troublesome and unhappy experience into a natural doorway to the spiritual dimension of existence.
[...] Women who practice yoga regularly have found that period pain is eased almost immediately and completely eliminated within a few months. They are generally more relaxed and overall health and vitality is increased.
Yogic Management of Common Diseases by Dr Swami Karmananda MBBS (Sydney) Under the guidance of Swami Satyananda Saraswati
Published by Bihar School of Yoga 1983, 2010