Herbs also not only contain many different varieties of nutrients and vitamins which are essential to the body, they facilitate the flow and growth of Qi and blood. According to TCM theory, as Qi and blood are invigorated in the womb, they create fertile ground for seeds to grow and flourish. They could also be helpful for women who have lost muscle tone from repeated childbirths. Studies from China have suggested the effectiveness of herbal treatment in the areas of luteal phase defect, endometriosis, immunological infertility and male infertility.