With cervical Incompetence (CI) the cervix starts to shorten (efface) and dilate too early in the pregnancy giving rise to late (2nd trimester) miscarriage or premature birth. It can occur with first pregnancies (“Primary Cervical Incompetence”) or after a prior pregnancy (“Secondary Cervical Incompetence”). CI often occurs in women who give a history of cervical insufficiency in one or more prior pregnancies; late miscarriages or premature deliveries of unknown cause; cervical injury during a previous birth or dilation and curettage (D&C); congenital uterine abnormalities such as a partial/complete uterine septum / unicornuate uterus; prior conization or a LEEP procedure done for an early (pre)cancerous condition affecting the cervix or in women with a multiple pregnancy (twins or greater).
The diagnosis of CI is suspected when a woman in pregnancy that has advanced into the 2nd or early 3rd trimester presents with bleeding and low pain-grade contractions associated a bulging bag of membranes, frequently followed by a sudden gush of fluid per vagina and relatively rapid progression to complete expulsion of the fetus and placenta.
Threatened CI should be suspected by the detection of a partially dilated and shortened cervix with routine pelvic examination performed in the mid-trimester or early 3rd trimester.
When during the non-pregnant state there is suspicion of CI, this should be investigated through the performance of one or more of the following:
A hysterosalpingogram (HSG-dye x-ray test) to evaluate for a well demarcated anatomical transition from endocervical canal to the uterine cavity (without evidence of “funneling”) and to detect a deformity (congenital or acquired) of the uterus, that can also lead to mid- trimester miscarriage and premature birth.
A vaginal ultrasound examination to measure the length of the cervical canal (it should measure more than 2.5 cm) and to exclude pathology of uterine wall (e.g.; fibroids)
A diagnostic hysteroscopy to carefully evaluate uterine scarring, fibroid tumors protruding into or distorting the uterine cavity and for the congenital deformities such as a uterine septum.
Cervical incompetence is routinely treated by the placement of a temporary circumferential non-absorbable tape or suture around the neck of the cervix at the 12th-14th week of pregnancy per vagina (“McDonald cerclage”. The advantage of this approach is that the cerclage can readily be removed a week or two before delivery, thereby allowing a subsequent spontaneous vaginal birth to take place The disadvantage of placing a McDonald cerclage” is the ever present risk of puncturing the fetal membranes while inserting the stitch. This sometimes prompts the overcautious OB/GYN to place the stitch well below the cervical-uterine junction, thereby increasing the likelihood that it will slip or tear and thus fail to prevent cervical shortening and dilatation.
After undergoing a preliminary assessment to confirm the diagnosis of cervical incompetence, non-pregnant women in whom a McDonald cerclage has failed, should be considered for the elective placement of a permanent, non-absorbable cerclage “Shirodkar suture”(, prior to undertaking another pregnancy. In fact I believe that this should be considered as the primary (initial) approach. The reason is that in the absence of a pregnancy, it is possible, through careful surgical dissection, to ensure the correct placement of the suture (usually a double strand of #2 nylon is used), and in so doing, maximize its effectiveness. The one relative disadvantage to this approach is that the completely buried Shirodkar suture, is sometimes not amenable to removable before delivery. Accordingly, such women would require delivery by Cesarean section. Notwithstanding this, we hold that a Cesarean delivery, is a relatively small price for a woman who has usually experienced recurrent pregnancy loss, and/or repeated premature deliveries, to pay to have a healthy baby.