Tibetan Medicine has a detailed description of conception and of the formation of the embryo: [...] the perfect semen, the menstrual blood and the mind of the intermediate state (bar-do), propelled by the right karma.
If the mind that is in the bar-do identifies itself with the semen, it is attracted by the mother and doesn’t like the father, it will be born as a boy. It identifies with the menstrual blood of the mother, that must be on the right time, and feels angry at the mother, it will be a girl. It is essential that the attraction for one parent and hate for the other must be felt, so that a new body is formed. If none of those feelings occur, there is no conception.
In addition to the semen, the menstrual blood and consciousness, the five elements are necessary: earth, water, fire, air and space. Earth helps the embryo to be solid; water helps it to be together; fire to be mature; air helps it to grow and space helps it to move. The earth generates muscle tissue, bones, the nose and the sense of olfact. Water generates the body fluids, the tongue and the sense of taste. Fire generates warmth, the appearance, the eyes and the sense of vision. The air generates breathing, the skin and the sense of tact. Space generates the different orifices, among them the ears and the sense of hearing.
Like the Chinese and the Hindu, that consider in their anatomy the channels of circulation of the vital forces, the chi and the prana, respectively, the Thibetans call the tsá channels, where the liquids circle, like blood and semen, and the “life wind” of lung or air. The air is the everpresent element and is related to the feelings; it is compared to the sky. From the moment of the conception onwards, the mind of the embryo spreads a “wind of life”. During the first week of existence of the embryo the father’s semen and the conscience mix themselves in every particle of the mother’s blood, like the milk when it transforms itself in yoghurt.
The development of the embryo takes 38 weeks. Until the 9th week, it has the shape of a fish and the members are not visible; from the 10th to the 17th week, the stage of the turtle, the embryo has this animal’s shape; the members appear, as well as the five solid organs, the six hollow organs, the sense organs, the connective nerves and the channels. From the 8th until the 35th week, the embryo is complete. It is called the stage of the pig, because the embryo can feel dirt in his environment. In the 26th week memory appears; the mind is clear and can remember its past life and look towards the future. In the 36th week the child looses its clarity of memory.
After the 38th week the embryo stands on its head and it is ready to be born.