Cervical insufficiency (formerly called cervical incompetence) is painless cervical dilation resulting in delivery of a live fetus during the 2nd trimester. Transvaginal cervical ultrasonography during the 2nd trimester may help assess risk. Treatment is reinforcement of the cervical ring with suture material (cerclage).

Cervical insufficiency refers to presumed weakness of cervical tissue that contributes to or causes premature delivery not explained by another abnormality. Estimated incidence varies greatly (1/100 to 1/2000).

Etiology

The cause 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 risk factors; however, the following risk factors have been identified:

• Congenital disorders of collagen synthesis (eg, Ehlers-Danlos syndrome)
• Prior cone biopsies (particularly when ≥ 1.7 to 2.0 cm of the cervix was removed)
• 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)
• ≥ 3 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 ≥ 3 prior 2nd-trimester fetal losses.

Symptoms and Signs

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

• Transvaginal ultrasonography at > 16 wk for women with symptoms or risk factors

The diagnosis is suspected in women with risk factors or characteristic symptoms or signs. Then, transvaginal ultrasonography is done. Results are most accurate after 16 wk gestation. Suggestive ultrasonographic findings include cervical shortening to < 2.5 cm, cervical dilation, and protrusion of fetal membranes into the cervical canal.

Ultrasonography of women without symptoms or risk factors is not recommended because results do not accurately predict preterm delivery.

Treatment

• Cerclage

Cerclage (reinforcement of the cervical ring with suture material) appears to prevent preterm delivery in patients with ≥ 3 prior 2nd-trimester fetal losses. For other patients, the procedure should probably be done only if they have a history strongly suggesting cervical insufficiency and if cervical shortening is detected by ultrasonography before 22 to 24 wk gestation; restricting cerclage to such patients does not appear to increase risk of preterm delivery and reduces the number of cerclages currently being done by two thirds. Evidence does not support use of cerclage simply for ultrasound-detected cervical shortening.

Treatments such as corticosteroids, progesterone, and bed rest are often used when preterm labor is suspected.

Last full review/revision February 2010 by Antonette T. Dulay, MD