Cervical insufficiency (cervical incompetence) is defined by the American College of Obstetricians and Gynecologists (ACOG) as the inability of the uterine cervix to retain a pregnancy in the second trimester, in the absence of uterine contractions. 
Signs and symptoms
The diagnosis of cervical insufficiency is primarily based on a history of a previous midtrimester pregnancy loss, which can present with the following:
Painless cervical dilatation and bulging fetal membranes upon presentation in the second trimester of pregnancy
Preterm premature rupture of membranes (PPROM)
Rapid delivery of a previable infant
Rare or absent uterine contractions
In women without a history of pregnancy loss, the diagnosis of cervical insufficiency is based on a combination of the following:
Most patients are asymptomatic, but some may present with any the following symptoms:
Increased vaginal discharge
See Presentation for more detail.
Although the diagnosis of cervical insufficiency may be based on a history of midtrimester pregnancy loss, the following measures may also be useful:
See Workup for more detail.
According to a 2014 practice bulletin from the ACOG concerning the management of cervical insufficiency, cervical cerclage, in which a stitch is placed at the cervicovaginal junction, may benefit women with a history of cervical insufficiency or painless cervical dilatation in the second trimester on physical examination. 
Cervical cerclage is the mainstay of surgical treatment for cervical insufficiency and is reasonable in the following situations  :
History of second trimester pregnancy loss with painless cervical dilatation
Prior cerclage placement for cervical insufficiency
History of spontaneous preterm birth (prior to 34 weeks’ gestation) and a short cervical length (ie, < 25 mm) prior to 24 weeks’ gestation
Painless cervical dilatation on physical examination in the second trimester
The ACOG does not recommend cerclage placement for women with a short cervix who do not have a history of preterm delivery, as it has not been shown to be beneficial in this population. Moreover, cerclage is not recommended for twin pregnancies with a short cervix, as this has been associated with an increased risk for preterm birth. Certain lifestyle approaches, such as activity restriction, bed rest, and pelvic rest, have not been shown to be effective and thus, should not be used to treat cervical insufficiency. 
Cerclage can be accomplished either transvaginally or transabdominally. The 2 most common transvaginal techniques are as follows:
McDonald cerclage (see the image below)McDonald cerclage.
Shirodkar cerclage (see the image below)Shirodkar cerclage.
Preoperative evaluation should include the following  :
Fetal ultrasound assessment for viability, gestational age, and any identifiable anomalies
Clinical evaluation to exclude active bleeding, preterm labor, and PPROM
Consideration of amniocentesis to rule out a subclinical intraamniotic infection, particularly in women with cervical dilatation at the time of presentation
Postoperative care should include consideration of the possible complications, including suture displacement, artificial rupture of membranes, and chorioamnionitis.
Although cervical cerclage has long been the focus of treatment, several studies support the use of progesterone supplementation in women at risk for preterm delivery. [7, 8, 9, 10, 11] In addition, the cervical pessary may be a potential alternative noninvasive treatment for cervical insufficiency, although further study is necessary. [12, 13, 14]
See Treatment for more detail.
Cervical insufficiency is defined by the American College of Obstetricians and Gynecologists (ACOG) as the inability of the uterine cervix to retain a pregnancy in the second trimester, in the absence of uterine contractions.  It typically presents as acute, painless dilatation of the cervix, which can lead to a midtrimester pregnancy loss. In women with this history, the risk of recurrence in a subsequent pregnancy is less than 30%. 
The cervix develops from fusion and recanalization of the distal paramesonephric (Müllerian) ducts, which is complete by approximately 20 weeks' gestation.  It is composed of both muscle and fibrous connective tissue, yet the fibrous component is responsible for the tensile strength of the cervix.  Cervical insufficiency is thought to be related to a structural defect in tensile strength at the cervicoisthmic junction, but other disorders (eg, decidual inflammation, intrauterine infection, hemorrhage, uterine overdistension) may result in premature cervical shortening, ultimately leading to preterm delivery. [18, 19]
Cervical insufficiency may occur as a result of a functional defect in the cervix, which can be due to an anatomic abnormality (congenital Müllerian anomalies), in utero exposure to diethylstilbestrol (DES), or collagen disorders (Ehlers-Danlos syndrome). [20, 21, 22, 23] Acquired causes of cervical insufficiency include obstetric trauma (eg, cervical laceration during labor and delivery), mechanical dilation of the cervix during gynecologic procedures, and cervical conization, which may be performed via cold knife, laser, or loop electrosurgical excision procedure (LEEP). [24, 25, 26, 27] A history of pregnancy termination is also associated with an increased risk of preterm birth, particularly for those women with more than one pregnancy termination. [28, 29] However, in many women, the cause of cervical insufficiency is unknown.