Cervical insufficiency is painless cervical dilation resulting in 2nd-trimester pregnancy loss in the absence of clinical contractions, labor, or both. Estimated incidence varies greatly (1/100 to 1/2000).
Etiology of Cervical Insufficiency
The cause of cervical insufficiency is not well-understood but seems to involve some combination of structural abnormalities and biochemical factors (eg, inflammation, infection); these factors may be acquired or genetic.
Risk factors
Most women with cervical insufficiency do not have known risk factors; however, the following risk factors have been identified:
Multiple gestation
Congenital disorders of collagen synthesis (eg, Ehlers-Danlos syndrome Ehlers-Danlos Syndromes Ehlers-Danlos syndromes are hereditary collagen disorders characterized by joint hypermobility, dermal hyperelasticity, and widespread tissue fragility. Diagnosis is clinical. Treatment is supportive... read more
)Prior cone biopsy (particularly when ≥ 1.7 to 2.0 cm of the cervix was removed) or trachelectomy
Prior deep cervical lacerations (usually secondary to vaginal or cesarean delivery)
Prior excessive or rapid dilation with instruments (now uncommon)
Müllerian duct defects (eg, bicornuate or septate uterus)
≥ 2 prior fetal losses during the 2nd trimester
Recurrence
Overall risk of recurrence of fetal loss due to cervical insufficiency is probably ≤ 30%, leading to the question of how large a role fixed structural abnormalities have. Risk is greatest for women with ≥ 2 prior 2nd-trimester fetal losses.
Symptoms and Signs of Cervical Insufficiency
Cervical insufficiency is often asymptomatic until premature delivery occurs. Some women have earlier symptoms, such as vaginal pressure, vaginal bleeding or spotting, nonspecific abdominal or lower back pain, or vaginal discharge.
The cervix may be soft, effaced, or dilated.
Diagnosis of Cervical Insufficiency
Transvaginal ultrasonography at ≥ 15 to 16 weeks for women with symptoms or risk factors
Usually, cervical insufficiency is not identified until after the patient has had at least one delivery after 15 weeks (1 Diagnosis reference Cervical insufficiency (formerly called cervical incompetence) is painless cervical dilation resulting in 2nd-trimester pregnancy loss. Transvaginal cervical ultrasonography during the 2nd trimester... read more 
).
The diagnosis of cervical insufficiency is suspected in patients with risk factors or characteristic symptoms or signs.
If there is uncertainty about the clinical suspicion of cervical insufficiency, patients may be monitored starting at 15 to 16 weeks through 23 to 24 weeks with serial transvaginal ultrasonography to measure cervical length.
Suggestive ultrasonographic findings include
Cervical shortening to ≤ 2.5 cm
Cervical dilation
Protrusion of fetal membranes into the cervical canal
Diagnosis reference
1. American College of Obstetricians and Gynecologists (ACOG): ACOG Practice Bulletin No.142: Cerclage for the management of cervical insufficiency. Obstet Gynecol 123 (2 Pt 1):372–379, 2014. doi: 10.1097/01.AOG.0000443276.68274.cc
Treatment of Cervical Insufficiency
Cervical cerclage
Cervical cerclage is reinforcement of the cervical ring with nonabsorbable suture material. Cerclage appears to prevent preterm delivery in patients with ≥ 2 prior 2nd-trimester fetal losses. Cerclage may be indicated based on history alone (history-indicated cerclage) or based on ultrasonographic findings plus history (ultrasound-indicated cerclage [ 1 Treatment references Cervical insufficiency (formerly called cervical incompetence) is painless cervical dilation resulting in 2nd-trimester pregnancy loss. Transvaginal cervical ultrasonography during the 2nd trimester... read more ]).
History-indicated cerclage is usually performed in patients with a history that strongly suggests cervical insufficiency, typically a history ≥ 2 deliveries at 15 to 24 weeks. In these patients, cerclage is done during the 1st trimester or may be done before pregnancy.
For patients with an uncertain risk of cervical insufficiency who are monitored with serial ultrasonography to measure cervical length, cerclage is typically done if length is < 2.5 cm before 24 weeks. Restricting cerclage to such patients does not appear to increase risk of preterm delivery and avoids unnecessary cerclage procedures. Evidence suggests that cerclage may help prevent preterm delivery in women who have a history of idiopathic preterm delivery and whose cervix is < 2.0 to 2.5 cm long (2 Treatment references Cervical insufficiency (formerly called cervical incompetence) is painless cervical dilation resulting in 2nd-trimester pregnancy loss. Transvaginal cervical ultrasonography during the 2nd trimester... read more ).
If preterm labor is suspected after 22 to 23 weeks, corticosteroids (to accelerate fetal lung maturation) and modified activity (modified rest) may also be indicated (2 Treatment references Cervical insufficiency (formerly called cervical incompetence) is painless cervical dilation resulting in 2nd-trimester pregnancy loss. Transvaginal cervical ultrasonography during the 2nd trimester... read more ).
Treatment references
1. American College of Obstetricians and Gynecologists: ACOG Practice Bulletin No.142: Cerclage for the management of cervical insufficiency. Obstet Gynecol 123 (2 Pt 1):372–379, 2014. doi: 10.1097/01.AOG.0000443276.68274.cc
2. American College of Obstetricians and Gynecologists (ACOG): ACOG Practice Bulletin, No. 234: Prediction and prevention of spontaneous preterm birth. Obstet Gynecol 138 (2):e65-e90, 2021. doi: 10.1097/AOG.0000000000004479
3. Raju TN, Mercer BM, Burchfield DJ, Joseph GF Jr: Periviable birth: Executive summary of a joint workshop by the Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, American Academy of Pediatrics, and American College of Obstetricians and Gynecologists. Obstet Gynecol 123 (5):1083-1096, 2014. doi: 10.1097/AOG.0000000000000243
Key Points
Cervical insufficiency is painless cervical dilation resulting in 2nd-trimester pregnancy loss.
Usually, risk of cervical insufficiency cannot be predicted before a patient has a first premature delivery.
Do transvaginal ultrasonography after 15 to 16 weeks if women have risk factors or symptoms.
Findings that suggest the diagnosis are cervical shortening to ≤ 2.5 cm, cervical dilation, or protrusion of fetal membranes into the cervical canal.
Treat at-risk women with cervical cerclage.
