What causes cervical insufficiency in pregnancy?

From the Guidelines

Cervical insufficiency in pregnancy is often caused by a combination of factors, including previous cervical trauma, congenital uterine abnormalities, genetic factors, and multiple pregnancies, which can weaken the cervix and increase the risk of preterm birth. The exact cause of cervical insufficiency is often unknown, but several factors can contribute to this condition. Previous cervical trauma, such as surgical procedures like LEEP or cone biopsies for cervical dysplasia, cervical lacerations during childbirth, or dilation and curettage procedures, can weaken the cervix and increase the risk of insufficiency 1. Congenital uterine abnormalities, such as uterine septum or bicornuate uterus, can also lead to cervical insufficiency. Some women may have an inherently weak cervix due to genetic factors or connective tissue disorders like Ehlers-Danlos syndrome. Exposure to diethylstilbestrol (DES) in utero, though rare now, has been linked to cervical structural abnormalities. Multiple pregnancies can place extra pressure on the cervix, increasing the risk. Infections, particularly those affecting the reproductive tract, may weaken cervical tissue.

Risk Factors

• Previous cervical trauma
• Congenital uterine abnormalities
• Genetic factors
• Multiple pregnancies
• Infections affecting the reproductive tract
• Exposure to diethylstilbestrol (DES) in utero

Diagnosis and Treatment

According to the Society for Maternal-Fetal Medicine, a midtrimester cervical length (CL) of 25 mm can be used to diagnose short cervix in individuals with a singleton gestation with no previous history of spontaneous preterm birth 1. Vaginal progesterone is recommended to reduce the risk of preterm birth in asymptomatic individuals with a singleton gestation and a transvaginal CL of 20 mm diagnosed before 24 weeks of gestation. Regular transvaginal ultrasounds to monitor cervical length are essential for high-risk women, as recommended by the American College of Radiology Appropriateness Criteria 1.

Important Considerations

• Cervical cerclage is not recommended for individuals without a history of preterm birth who have a sonographic short cervix (10-25 mm) in the absence of cervical dilation 1.
• Cervical pessary is not recommended for the prevention of preterm birth in individuals with a singleton gestation and a short cervix due to potential safety concerns 1.

From the Research

Causes of Cervical Insufficiency in Pregnancy

• Cervical insufficiency is a condition where the cervix is unable to retain a pregnancy in the second trimester 2
• The exact cause of cervical insufficiency is not fully understood, but it is thought to be related to a combination of factors, including:
  • Prior history of preterm birth or mid-trimester miscarriage 3, 4
  • Short cervical length detected on ultrasound 3, 4
  • History of cervical surgery or trauma 2
  • Infections, such as bacterial vaginosis 3
• Women who have undergone trachelectomy are also at increased risk of cervical insufficiency 3

Risk Factors for Cervical Insufficiency

• Prior history of preterm birth or mid-trimester miscarriage 3, 4
• Short cervical length detected on ultrasound 3, 4
• History of cervical surgery or trauma 2
• Infections, such as bacterial vaginosis 3
• Multiple gestations 3, 4
• Women who have undergone trachelectomy 3

Diagnosis and Management of Cervical Insufficiency

• Diagnosis is typically made based on a combination of clinical history, physical examination, and ultrasound findings 3, 4
• Management options include:
  • Cervical cerclage 3, 4, 2, 5, 6
  • Vaginal progesterone therapy 5, 6
  • Bed rest and activity restriction 4
  • Serial ultrasound monitoring of cervical length 3, 4