An incompetent cervix is a cervix that dilates prematurely without labor or contractions. It occurs usually in the second trimester (12 to 22 weeks of gestation). It is a common cause of second trimester miscarriages. The cause is usually unknown but can be due to a history of cervical surgery (done to treat abnormal pap smear results) and congenital uterine anomalies. Multiple Dilation and Curettages (D & C) done for miscarriages or abortions can also weaken the cervix. If your health care provider diagnoses it early, a cerclage will often be recommended. This is a stitch that is applied around your cervical opening and then tied. It is usually done at the end of your first trimester and is left in you until the end of the pregnancy.