Is a small gestational sac in relation to the fetus a sign of a chromosomal abnormality. fetus 9w sac 7w. doctor and research have me very worried.

See doctor: It is a matter of concern -,may be chromosomal abnormality or with the formation of sac .Your doctor will keep a check on subsequent visit and on U/S finding about the growth of sac and fetus .

Hard to answer...: At such an early stage, imaging and interpretation is hard. There are associations between size and abnormalities. But it is impossible to look at a minimally smaller size and conclude anything, especially chromosomal disorders. It is best not to worry, but follow this serially and monitor progress. Your OB is the best judge of this and should advice you of intervention if at all needed.