are gestational sac and yolk sac the same
Gestational sac The yolk sac and embryo should be readily identifiable when the gestational sac reaches a certain size â€” a yolk sac should be seen when the gestational sac is 20mm and a fetal pole should be seen when the gestational sac reaches 25mm.
Fetus A fetus is a stage in the prenatal development of viviparous organisms. In human development, a fetus or foetus (/ˈfiːtəs/; plural fetuses or foetuses) is a prenatal human between the embryonic state and birth. The fetal stage of development tends to be taken as beginning at the gestational age of eleven weeks, i.e. nine weeks after fertilization.[1][2] In biological terms, however, prenatal development is a continuum, with no clear defining feature distinguishing an embryo from a fetus. The use of the term "fetus" generally implies that an embryo has developed to the point of being recognizable as a human; this is the point usually taken to be the ninth week after fertilization. A fetus is also characterized by the presence of all the major body organs, though they will not yet be fully developed and functional and some not yet situated in their final anatomical location.