From the time of conception till the zygote gets itself attached to uterus, its nutrition depends on the nutritive parts carried by sperms and ovum. 

Charaka says that with the normalcy of all six factors of conception and use of appropriate diet alongwith proper mode of life followed by the pregnant woman, the foetus thus obtaining its nourishment from rasa (supplied by mother) by the process of upasneha (attracting moisture) and upasweda (osmosis) and influenced time factor alongwith its own nature or desires grows normally. The foetus does not feel hunger and thirst and is totally dependent upon the mother.

• In initial stage when its specific body parts though present are not explicit, it obtains its subsistence by attracting moisture and osmosis.
   
• Afterwards when body parts are conspicuous, a part of nourishment is obtained by upasneha (moisture) permeating through pores of skin situated in hair roots of the body and a part through the passage of umbilical cord. The foetal umbilicus is attached to the umbilical cord, umbilical cord to the placenta and placenta to the mother's heart.
   
• The mother's heart immerses the placenta (with blood) through running and oozing vessels.
   
• Mother's diet contains all the rasas, thus the rasa derived from this diet gives strength and complexion to the foetus, and foetus deriving its sustenance from this diet remains alive and develops in the uterus. Caraka further explains the point that what so ever diet the pregnant woman consumes, the rasa formed from this performs three functions.
• nourishment of the woman's body,
• formation of milk 
• nourishment to the foetus.
   
• Vagbhata I adds that from umbilical cord the rasa reaches pakwasaya (digestive system) of the foetus and there with its own kayagni (digestive fire) it gets metabolized and provides nourishment to it. Since rasa carries pure nutrients, hence excreta are not formed.
   
• Indu has explained that unctuousness is upasneha and moistening is upasweda.
   
• Entire foetal nourishment is divided into two stages, before apparent evidence of organs or upto three months and after wards.
   
• Before implantation, zygote gets its nourishment from exudates of uterine cavity and after implantation but before complete placenta formation, through chorionic villi present all over the embryonic surface. This has very clearly been mentioned by Sushruta that embryo gets nourishment from the channels running all around it.