Identify women at risk of preterm birth
A cervical length ≤25 mm before 24 weeks is associated with a 3‑5 fold increased risk of spontaneous preterm delivery – making it an invaluable screening tool.
Cervical length assessment is a focused ultrasound examination that measures the length of the cervix – the lower part of the uterus that opens during labour. It is one of the most powerful predictors of preterm birth. A short cervix (typically ≤25 mm) is associated with a significantly increased risk of spontaneous preterm delivery, especially in women with a history of preterm birth or cervical insufficiency.
This assessment is usually performed via transvaginal ultrasound, which provides the most accurate and reproducible measurements. It is typically done between 16 and 24 weeks, often as part of the routine anomaly scan or as a targeted evaluation in high‑risk pregnancies. Early detection of a short cervix allows for interventions such as vaginal progesterone, cervical cerclage, or increased surveillance – which can reduce the risk of preterm birth and improve neonatal outcomes.
At Amytri, our cervical length assessments are performed by a consultant radiologist with advanced training in obstetric ultrasound. We use a standardised technique, measuring the closed cervical length from the internal to the external os. We provide a clear report with the measurement, and discuss the implications with you and your obstetrician – guiding the next steps in your care.
Preterm birth is the leading cause of neonatal morbidity and mortality. Cervical length assessment is a simple, non‑invasive way to identify women at risk and intervene early.
A cervical length ≤25 mm before 24 weeks is associated with a 3‑5 fold increased risk of spontaneous preterm delivery – making it an invaluable screening tool.
Women with a short cervix can benefit from vaginal progesterone, cervical cerclage, or bed rest – all shown to reduce preterm birth rates when used in selected cases.
A normal cervical length (≥30 mm) provides strong reassurance that the risk of spontaneous preterm birth is low – especially in women without prior risk factors.
We use a standardised transvaginal technique to obtain reliable and reproducible measurements.
We measure the straight‑line distance between the internal and external cervical os, along the endocervical canal. The measurement is taken from the best sagittal view, with gentle pressure to avoid compression.
We assess the presence and degree of funneling – the opening of the internal os. Funneling indicates early cervical dilatation and increases the risk of preterm delivery, even if the closed length is still >25 mm.
We evaluate the cervical index (funnel length / total cervical length) – a parameter that may be used to further stratify risk, though not universally applied.
We may apply gentle pressure on the cervix to assess for dynamic shortening – a finding that can indicate cervical insufficiency, even if the baseline length is normal.
While not part of the ultrasound, we may discuss combining cervical length with FFN testing (if clinically indicated) for enhanced risk prediction.
If the cervix is borderline or short, we recommend serial assessments (every 1‑2 weeks) to track changes and guide therapy.
Your obstetrician refers you – either as part of routine screening (especially with risk factors) or for targeted assessment if symptoms suggest cervical insufficiency.
A full bladder can artificially lengthen the cervix – we ask you to empty your bladder before the transvaginal scan for the most accurate measurement.
We use a small, sterile probe placed gently in the vagina. This gives the clearest view of the cervix. The scan is painless and takes about 10‑15 minutes.
We measure the cervical length and assess for funneling. We discuss the result with you and your obstetrician – recommending progesterone, cerclage, or serial monitoring as appropriate.
It is routinely offered to women with risk factors for preterm birth, but may also be performed for reassurance in uncomplicated pregnancies.
A history of spontaneous preterm delivery is the strongest risk factor – cervical length screening is recommended in subsequent pregnancies.
If you have had a pregnancy loss in the second trimester or a diagnosis of cervical insufficiency, serial cervical length monitoring is essential.
Multiple pregnancies are at increased risk of preterm birth – cervical length assessment is often performed serially.
Conditions like a uterine septum, cervical cone biopsy, or LEEP procedure can increase the risk of cervical insufficiency – monitoring is recommended.
Symptoms like pressure, backache, or vaginal discharge may prompt an assessment to rule out cervical shortening.
In some settings, universal cervical length screening at 18‑22 weeks is performed – a normal result offers strong reassurance.
Cervical length measurement requires a standardised technique to avoid false results. Our consultant radiologist has extensive experience in transvaginal ultrasound and preterm birth risk assessment, ensuring accurate and reliable measurements that guide your obstetrician's management decisions.
Cervical length assessment is a quick but important test – having your partner with you provides support and shared understanding.
While the transvaginal scan is performed in a private setting, your partner can be present if you wish. We explain the measurement and its significance, and answer any questions. If the cervix is short, we discuss the next steps – progesterone, cerclage, or extra monitoring – with sensitivity and clarity.
It is a transvaginal ultrasound that measures the length of the cervix. A short cervix (≤25 mm) is a strong predictor of preterm birth, and the measurement helps guide interventions to prevent early delivery.
Yes. It is a standard obstetric procedure that is safe for both mother and baby. The probe is sterile and inserted gently – it is not painful and does not affect the pregnancy.
No – we actually ask you to empty your bladder before the scan, as a full bladder can artificially lengthen the cervix and give a false reading.
The optimal timing is between 16 and 24 weeks. Serial measurements may be performed every 1‑2 weeks if the cervix is shortening or if you have risk factors.
We will discuss the results with you and your obstetrician. Treatment options include vaginal progesterone, cervical cerclage (if appropriate), and increased surveillance. These interventions can reduce the risk of preterm birth.
Yes, typically a referral from your obstetrician is required, especially if you have risk factors or symptoms. We will coordinate with your care team to provide the best management.
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