Blood deficiency (Xue xu) is an issue than women tend to get more than men simply because they lose blood each month and it takes energy to replace it. Blood is a precious substance for life and it’s essential for women (and men) to be at their most fertile.
“In women, it is Blood [which] makes [their] root [and] Qi which makes for function”
Blood has a number of functions; it’s an energy source that nourishes, forms and moistens the body tissues, skin and organs and plays an important and direct role in fertility by nourishing the growth of the womb lining so an embryo can successful implant. Blood’s stored in the Liver, and the Liver Blood nourishes the growth of the follicles in the ovaries and development of womb, so a deficiency of Liver Blood reduces the quantity and quality of blood that reaches the uterus and scanty, pale periods are a typical sign of this. Heart Blood deficiency can also affect fertility (and the timing of ovulation), but Liver Blood deficiency usually affects fertility more.
“The Blood within a woman’s Uterus is exchanged one time each month;
eliminating the old [and] engendering the new”
Although the uterus is nourished by Liver Blood the filling and emptying of the uterus through the menstrual cycle is controlled by the Extraordinary vessels; particularly the Ren Mai (Conception vessel) and the Chong Mai (Penetrating vessel).
“The eight [extraordinary] vessels home to the Kidneys”i
Of the Extraordinary vessels, the Chong, Ren, Du and Dai Mai originate in the Kidneys, with the Ren and Chong Mai having central roles in determining the rhythms and function of the uterus:
“the Ren [and] Chong arise within the Uterus”
“the Ren and Chong are rooted in the Blood and home to the Liver”
Any deficiency in the substances (Yin, Blood and Qi) that fill these vessels will impair their function and Blood is the substance that fills the Chong Mai in particular and any deficiency of Blood changes the function of the Chong Mai:
“The Chong Mai is the Sea of Blood”
“If the two vessels of the Chong [and] Ren [become] vacuous [and suffer] detriment…[they] will not be able to control and restrain the menstrual blood”
An abundance of Qi and Blood are needed to create new life, and the Ren and Chong Mai need to be full if theyre to regulate and control the uterus. Although Blood is stored in the Liver it has strong connections to the Kidneys, and the Yuan Qi of the Kidneys is needed to form Blood;
“the fountainhead of Blood is located in the Kidneys.”
However the Spleen is the main organ responsible for creating post-heavenly Qi and Blood;
“Blood is the essence of water [and] grain engendered [and] transformed by the Spleen”
This relationship between Spleen Qi and Blood is mutual:
“Qi is able to engender Blood”
“Blood is able to engender Qi”
Blood is the substance that nourishes and fuels Qi, and Blood deficiency will in time tend to lead to Qi deficiency. Spleen Qi (along with Yuan Qi) makes Blood via the transformation of food essences; when Spleen Qi is deficient it’s less able to make Blood, even from an adequate diet. When Qi or Blood are deficient or stagnant (or there’s excess Heat or Cold) the function of the Ren and Chong Mai become compromised, less able to regulate and nourish the uterus, which reduces the chances of conception and a healthy pregnancy.
iFrom Statements of Fact in Traditional Chinese Medicine by Bob Flaws. ISBN 0-936185-52-X