Cervical Length Screening
What is cervical length screening?
Ultrasound Care’s specialist team of obstetricians and sonographers conduct cervical length screening to assess the length of the cervix in pregnant women who are at high risk of a preterm delivery.
What is preterm birth?
The average pregnancy lasts approximately 40 weeks from your last menstrual period. This is called “term”. But some babies try to come earlier. Premature labour can result in preterm birth.
Sometimes, preterm babies are born before their organs are mature enough and they may need to be admitted to a newborn intensive care nursery for extra treatment. This occurs in about 6% of pregnancies and it is something we try to avoid.
The risk of spontaneous preterm birth increases as the length of the cervix (neck of the womb) decreases. The Ultrasound Care team can measure the length of the cervix in pregnant women accurately with trans-vaginal ultrasound examination.

A tiny premature baby in the neonatal intensive care unit
Why is cervical length screening used?
Ultrasound Care are often asked to assess the length of the cervix in women who are at high risk of preterm birth. Sometimes we have to do this on two or more occasions to see if there has been any change.

What is a normal cervical length?
The length of the cervix changes with advancing gestation.
- At 20 weeks gestation the average cervical length is about 40mm but there is wide variation.
- If the length is less than 25 mm it indicates a higher risk of preterm birth
- If the length is less than 15 mm it is clearly abnormal. We will discuss the situation with your doctor or midwife.
Who may be asked to have cervical length screening?
Ultrasound Care provides cervical length screening for all women who come for a 19-20 week scan, unless they advise they do not want it. We do this as the evidence shows that about 45% of preterm births can be prevented with treatment if a short cervix is detected in time.
Who is at higher risk of premature labour?
Women who are at higher risk of premature labour are often asked to have screening performed at their routine 18-20 week scan and later. This includes:
- Women who have had a previous premature delivery.
- Women who have had previous surgery on their cervix.
- Women with an uncommon uterine shape.
- Women with a cervical suture.
- Women who have had a painless second trimester fetal loss.
- Women with multiple pregnancies may also benefit from cervical screening.
How do I arrange for cervical length screening ultrasound?
Ultrasound Care provides cervical length screening for all women at their 19-20 week ultrasound unless they advise us that they do not want this. When you book in for your 19-20 week ultrasound, please ask our team if you have any questions regarding cervical length screening. Our team provides this ultrasound at each of our 8 locations in Sydney, so please choose a location that is most convenient to you.