Chorion is one of the extraembryonic membranes that surround the fetus and the amniotic cavity. The cells present in the chorion have the same genome and chromosomes as present in the fetus. Therefore, some of the chorionic tissues are collected from the chorionic villi. These tissues are then analyzed for any chromosomal abnormality. This process is called chorionic vill sampling. For the purpose, tissue collection can be done by inserting a catheter through the cervix or using a needle through the uterine wall.
