Cervical Incompetence: What It Is, How It Is Diagnosed, and How Cerclage Helps
Medical illustration depicting Cervical Cancer; depicts a woman's body with a diagram of the pelvis showing the cervix in section as well as a magnified uterus clearly showing cancerous growths and HPV.
Cervical incompetence — also called cervical insufficiency — is a condition where the cervix weakens and begins to open (dilate and efface) in the second trimester of pregnancy without the usual warning signs of contractions or labour. The result is a pregnancy loss or extremely premature birth at a gestational age when survival is unlikely or uncertain.
It is a devastating but — once identified — often preventable cause of second-trimester loss and extreme preterm birth.
Dr. Shachi Singh, consultant obstetrician at Prakash Hospital, Sector 33, Noida, explains.
What the Cervix Normally Does in Pregnancy
Throughout pregnancy, the cervix acts as a firm, closed barrier — maintaining the structural integrity of the pregnancy above it. It remains long (typically 3 to 4 cm), closed, and firm until the body initiates labour at term. The transition from closed to open occurs over hours to days in normal term labour.
In cervical incompetence, this transition happens silently — without contractions — in the second trimester, typically between 14 and 24 weeks. The cervix opens painlessly, the membranes prolapse through the opening, rupture occurs, and a non-viable or periviable delivery follows.
Causes and Risk Factors
Previous cervical trauma:
- Previous LEEP/LLETZ procedures for CIN — particularly large excisions or multiple procedures
- Cervical cone biopsy
- Traumatic cervical dilation during D&C (curettage) procedures
- Forceful dilation of the cervix during termination of pregnancy
Congenital factors:
- Müllerian duct anomalies — a bicornuate or septate uterus is often associated with a shorter or weaker cervix
- Connective tissue disorders — Ehlers-Danlos syndrome
Previous second-trimester pregnancy loss: Particularly if it was silent — no contractions before membrane rupture — which is the classic presentation of cervical incompetence.
In vitro fertilisation: Slightly higher risk of cervical incompetence and preterm birth, though exact mechanisms are debated.
Diagnosis
History: The most important diagnostic tool. A history of one or more second-trimester losses (14 to 24 weeks) with no preceding contractions — just silent cervical opening — is highly suggestive.
Transvaginal cervical length ultrasound: Measuring the cervical length on transvaginal ultrasound is the key diagnostic tool in current pregnancies at risk. A cervical length below 25 mm at 16 to 24 weeks is associated with significantly elevated preterm birth risk. Funnelling (the internal os opening in a U or V shape while the external os remains closed) is a further sign of cervical incompetence.
Cervical length monitoring is recommended from 14 to 16 weeks in all women with:
- History of second-trimester loss
- Previous preterm birth below 34 weeks
- Previous significant cervical surgery (LEEP, cone)
- Müllerian anomalies
Treatment: Cervical Cerclage
Cervical cerclage is a procedure where a stitch (suture) is placed around the cervix to mechanically reinforce it and prevent premature opening.
Types of cerclage:
History-indicated cerclage (elective cerclage): Placed prophylactically at 12 to 14 weeks based on a history of cervical incompetence (two or more second-trimester losses or one preterm birth with cervical incompetence). Does not wait for cervical shortening to occur — placed before any evidence of incompetence in the current pregnancy.
Ultrasound-indicated cerclage: Placed when cervical length falls below 25 mm on surveillance ultrasound between 16 and 24 weeks — in a woman with a history of previous preterm birth. The CIPRACT and similar trials support this approach.
Emergency (rescue) cerclage: Placed when the cervix is already dilated and the membranes are visible at the os but have not yet ruptured. A technically demanding procedure with more limited evidence but can significantly prolong the pregnancy in selected cases.
The procedure: Performed under regional or general anaesthesia, typically as a day procedure or with overnight stay. The McDonald cerclage (the most commonly used technique) places a purse-string suture around the cervix. The Shirodkar cerclage places the suture higher up at the internal os. The cerclage suture is removed at 36 to 37 weeks (or earlier if labour begins) and vaginal delivery proceeds normally.
Additional Interventions
Vaginal progesterone pessaries: 200 mg micronised progesterone nightly from 16 weeks — for women with a short cervix identified on surveillance. Evidence from multiple trials supports vaginal progesterone reducing preterm birth risk in women with a cervical length below 25 mm, particularly as a singleton pregnancy.
Arabin pessary: A silicone pessary placed around the cervix to redistribute the load of the pregnancy — an alternative or addition to cerclage in some settings.
Obstetric Care in Noida and Greater Noida
Dr. Shachi Singh at Prakash Hospital, Sector 33, Noida, manages cervical incompetence and high-risk pregnancies — including cervical length surveillance, cerclage placement, and progesterone therapy — for women across Noida and Greater Noida.
To book a consultation with Dr. Shachi Singh, call: +91 97023 46853
Clinic Hours: Monday to Saturday, 9 AM – 6 PM | Sunday, 10 AM – 2 PM
Clinic Address: D-12A, 12B, Sector-33, G.B. Nagar, Noida, Uttar Pradesh 201301
This blog is written for educational purposes only. Please consult Dr. Shachi Singh for assessment specific to your obstetric history.
