I have read a lot about this lately since it happened to me and here is what I understand about it.
Incompetant cervix is a cervix that is too weak to stay closed during a pregnancy. It can cause preterm birth and depending on how far along the pregnancy is it can cause loss of the baby too.
I was only 22 weeks and generally infants this premature do not survive, unfortunatly.
I have posted my story on the miscarriage board if you are interested in reading it here is a link -http://www.soulcysters.net/showthread.php?s=&threadid=48587
There is hope though, they have procedure called cerclage. There are different types but they all basically do the same thing by stitching the uterus shut to prevent the cervix from opening too soon, thus hopefully keeping the baby in long enough to survive.
If anyone else has more information or a success story please post. Encouragement is always welcome!!