Cervical Insufficiency

Summary

Cervical insufficiency is painless cervical dilation leading to recurrent second-trimester losses or preterm birth, usually due to cervical trauma or congenital weakness. Diagnosis is based on history and transvaginal ultrasound showing short cervix, while management is cervical cerclage (McDonald, Shirodkar, or transabdominal) placed electively at 12–14 weeks or urgently if indicated, achieving 85–90% success. Contraindications include labor, advanced dilation, ruptured membranes, and infection.

Definition

 Cervical insufficiency, also referred to as cervical incompetence, is the inability of the uterine cervix to retain a pregnancy until viability in the absence of uterine contractions or labor. It typically presents as painless cervical dilation leading to recurrent second-trimester pregnancy losses or preterm birth.

Etiology and Risk Factors

Cervical insufficiency may result from acquired or congenital causes:

• Acquired causes (most common):

• Trauma from rapid cervical dilation during second-trimester abortion procedures

• Cervical lacerations following precipitous delivery or forceps-assisted breech extraction

• Cervical injury after deep conization or loop excision procedures

• Congenital causes:

• In utero exposure to diethylstilbestrol (DES)

• Intrinsic cervical weakness

• Other risk factors: multiparity, altered hormonal balance (↑estrogen, ↑relaxin, ↓progesterone).
  

Pathophysiology

The normal cervical length is approximately 4 cm. A cervical length <2 cm is considered incompetent. Progressive, painless dilation exposes the fetal membranes to vaginal flora and trauma, increasing the risk of premature rupture of membranes (PROM), intrauterine infection, and preterm labor.

Clinical Features

• Typical presentation: painless, recurrent second-trimester pregnancy loss

• Symptoms and findings:

• Sudden gush of fluid due to rupture of membranes

• Passage of products of conception without preceding labor

• Vaginal bleeding or discharge in some cases

• Examination/Imaging:

• Speculum exam: dilated cervix with bulging membranes

• Transvaginal ultrasound: short cervical length or funneling

• Routine ultrasound may incidentally detect cervical changes

Diagnosis

• Pregnant women:

  • Serial transvaginal sonography between 14–26 weeks to monitor cervical length and funneling

• Non-pregnant women:

  • Hysterosalpingography (HSG) in the follicular phase, useful in evaluating recurrent second-trimester pregnancy loss
    

Management

Cervical Cerclage

Placement of a reinforcing suture around the cervix is the standard treatment, with a success rate of 85–90%.

• Timing:

• Prophylactic (elective): at 12–14 weeks after confirming fetal normality

• Urgent/emergency: during pregnancy if cervical shortening or dilation is detected, provided labor and chorioamnionitis are excluded

• Types:

• Transvaginal Cerclage (TVC):

• McDonald technique: removable suture at cervicovaginal junction; allows for vaginal delivery. Suture is removed at 36–37 weeks.

• Shirodkar technique: submucosal suture at internal os, buried beneath mucosa; typically requires cesarean delivery.

• Transabdominal Cerclage (TAC):

• Indicated after failed TVC or in cases of severely damaged cervix

• Permanent; delivery must be by cesarean section

• Complications: infection, vaginal discharge, PROM, preterm labor, cervical lacerations

• Indications for removal of cerclage before term: onset of labor (most common), ruptured membranes, infection, intrauterine fetal death

• Contraindications: active labor, cervical dilation >3 cm, ruptured membranes, chorioamnionitis
  
  

Prognosis

With appropriate cerclage, the majority of patients achieve successful pregnancies, significantly reducing the recurrence of second-trimester pregnancy loss. Transabdominal cerclage remains an option for refractory cases.