Funneling is the term used to describe when the amniotic sac moves into the cervix prematurely, forcing the cervix to take on the shape of a funnel. The band used for a TAC is tied with enough tension to prevent funneling without compromising the blood flow of the cervix. A TAC, however, cannot fix a cervix that has already funneled. In rare circumstances, funneling below the TAC can occur if it could not be optimally placed due to a physical abnormality – such as a fibroid near the top of the cervix – or cervical tissue that has been damaged by a surgical procedure or a tear from a previous childbirth.