What does cervical shortening mean?
The cervix normally remains firm and closed during pregnancy. As labour approaches it naturally softens, shortens, and opens. When shortening occurs early—particularly before 24 weeks—it may be associated with a higher risk of spontaneous preterm birth.
A “short cervix” is an ultrasound finding, not a prediction that preterm birth will definitely occur. Risk depends on gestational age, measured length, prior pregnancy history, whether the pregnancy is singleton or multiple, cervical dilation, and other clinical findings.
What can cause a short cervix?
- Previous spontaneous preterm birth or second-trimester pregnancy loss;
- Previous excisional surgery on the cervix;
- A congenital uterine or cervical difference;
- Multiple pregnancy and greater uterine distension;
- Congenital or acquired cervical weakness;
- In some cases, infection, bleeding, or contractions.
Often, however, no single cause is identified.
Does a short cervix cause symptoms?
Cervical shortening is frequently symptom-free and detected only by ultrasound. Possible symptoms include pelvic pressure, a dull lower backache, recurrent abdominal tightening, a change in vaginal discharge, spotting, or watery fluid.
These symptoms are not specific, but they should not be ignored. Contact maternity care urgently for regular contractions, bleeding, or suspected rupture of membranes.
How is cervical length measured?
Transvaginal ultrasound cervicometry is the standard, most reproducible method. It is performed with an empty bladder, usually takes only a few minutes, and does not harm the fetus. The specialist measures the closed cervical length and checks the internal opening, any funneling, dilation, and the membranes.
In a singleton pregnancy during the mid-trimester, 25 mm or less is commonly used to define a short cervix. A number must not be interpreted in isolation: gestational age, technique, symptoms, and obstetric history all affect management.
What are the risks?
A shorter cervix increases the probability of preterm birth, but individual outcomes vary. Earlier and more marked shortening, especially with dilation, warrants prompt specialist review. Read more about risk factors for preterm birth.
How is a short cervix managed?
Management may include:
- Vaginal progesterone in selected singleton pregnancies when a short cervix is diagnosed before 24 weeks;
- Cervical cerclage in selected patients, particularly with a relevant obstetric history or cervical dilation;
- Repeat cervicometry to monitor change;
- Assessment for contractions, infection, bleeding, or membrane rupture when symptoms are present.
Routine strict bed rest is not an effective treatment for every patient and may have its own risks. Progesterone, a pessary, cerclage, or activity restriction must be prescribed by the obstetric specialist managing the pregnancy.
Why does specialist technique matter?
Bladder filling, pressure from the probe, measurement duration, and a temporary uterine contraction can alter the apparent length. Standardised technique is therefore essential. Radiologist Lana Ezieshvili assesses cervical length, the internal os, and other relevant obstetric ultrasound findings.
If cervicometry has been recommended, you have a history of preterm birth, or you have concerning symptoms, book an appointment with Lana Ezieshvili. A timely, correctly performed scan helps your obstetrician choose the appropriate management plan.