The fetal membranes consist of the chorion, amnion, yolk sac, and allantois. The chorion has three layers: cytotrophoblastic, chorionic connective tissue, and basement membrane. The chorion lies ...

However, a gestational sac can be identified on transvaginal ... on the evacuated uterine contents to look for the presence of chorionic villi. If chorionic villi are identified, the diagnosis ...