Cervical / Cervix Length Ultrasound Scans 14-36 weeks of pregnancy

What is a cervical scan?

The cervical scan is an ultrasound test that is used to check the length of your cervix during pregnancy. The cervix is the passage at the opening of your womb. It will change as the pregnancy progresses in order to keep your baby safe and then to prepare for the delivery. We can measure the cervix during a trans-vaginal ultrasound to ensure it is within the normal range. If it is too short, then you may be at risk of complications such as a premature delivery.

Why this scan?

  • Checks the length of the cervix
  • Assesses the risk of premature birth
  • Investigate symptoms such as loss of amniotic fluid

What you will receive

  • Results of the cervical length measurement
  • Full ultrasound report for your maternity notes
  • Scan pictures for your medical records

When Should You Have a Cervical Scan?

The cervical scan is usually recommended if you are at risk of a premature delivery or there is reason to believe your cervix might be weaker than normal. Your midwife or obstetrician may refer you to us for a cervical scan if you have previously given birth early or had any issues with your cervix. You may need a cervical length scan if you were diagnosed with cervical incompetence during a previous pregnancy or you’ve had cervical surgery in the part. Cervical scans can also be performed to investigate symptoms such as loss of amniotic fluid.

The results will tell us whether your cervix is within the normal range for this stage in your pregnancy. If it is, then is should reassure you that you are at no higher risk of complications or early delivery. If an issue is detected, then there are steps your antenatal care team can take to reduce the risks. You will need to discuss the results with your obstetrician or midwife.

What to Expect

  • Cervical scans are usually performed between 16 and 21 weeks, but they can be done at any time between 14 and 36 weeks. We often recommend having two scans a few weeks apart, so we can monitor any changes in the cervix.
  • We will need to perform a trans-vaginal ultrasound to get clear pictures of your cervix. A slim ultrasound probe will be inserted into your vagina, so you’ll need to remove the lower half of your clothing. You should also empty your bladder when you arrive at the clinic for your appointment.
  • The cervix should usually be more than 25mm long at 17-21 weeks. If we find that it is shorter than expected, then you may be at higher risk of a premature delivery. Your sonographer will be able to discuss the results with you and you should talk to your midwife or obstetrician too as you may need treatment to reduce the risk.

Arranging Your Cervical Scans

This scan is only available as part of a Reassurance scanAnomaly Scan or Wellbeing Scan

Patient Information

Some early pregnancy ultrasound scans are performed using a transvaginal probe technique. This technique is used to view the pelvic anatomy optimally, as the ultrasound probe can transmit safe ultrasound waves more directly to the pelvic area. In later stages of pregnancy, it may be advised to perform a transvaginal ultrasound scan to have a closer look at a baby’s anatomy, or to assess the maternal cervix.

There is no clinical risk associated with performing a transvaginal ultrasound scan. Transvaginal ultrasound scans can safely be performed during episodes of vaginal bleeding. 

It is important that you understand the procedure that is associated with this examination.

  • The ultrasound transducer will be placed in the vagina (the probe is prepared using high grade medical disinfectant)
  • The transducer will be introduced with a latex / non latex type covering and sterile ultrasound gel.
  • It will be necessary to move the transducer from side to side, up and down and may be swivelled to obtain ultrasound images of your pelvic anatomy.
  • If you prefer, you may insert the transducer yourself, otherwise the person conducting the examination will do this.
  • A third person may be present during the examination acting as a chaperone, if required by the sonographer or yourself.
  • You may request the examination to be stopped at any time during the procedure.


If you are a virgin (Virgo intacta; hymen intact), guidance determines that transvaginal ultrasound scans are clinically contraindicated. If you have discussed this concern with your referrer and wish to proceed with a transvaginal ultrasound scan, this type of examination can be performed.

Should I get the COVID-19 Vaccine in pregnancy?

COVID-19 vaccines are strongly recommended in pregnancy. Vaccination is the best way to protect against the known risks of COVID-19 in pregnancy for both women and babies. Women may wish to discuss the benefits and risks of having the vaccine with their healthcare professional and reach a joint decision based on individual circumstances.

Frequent questions regarding the COVID-19 Vaccine

Find below a link to a Q&A from the Royal College of Obstetricians and Gynaecologists regarding Covid-19 Vaccines, pregnancy, and breastfeeding.

COVID-19 Vaccines, pregnancy and breastfeeding  

COVID-19 Information Sheet and Decision Aid

Clinic Locations

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137 Harley Street,
London W1G 6BF

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Baker Street
Regent’s Park
Great Portland Street

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Alderley Edge Medical Centre, Talbot Road, Alderley Edge,
Cheshire, SK9 7HR

Nearest Overground Train Station Alderley Edge

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Harley Street, London

The Birth Company
137 Harley Street

020 7725 0528

Harley Street, London Opening Times

Mon 08:00 - 20:00
Tue 08:00 - 20:00
Wed 08:00 - 20:00
Thu 08:00 - 20:00
Fri 08:00 - 18:00
Sat 09:00 - 16:00
Sun 10:00 - 14:00

Alderley Edge, Cheshire

The Birth Company
Alderley Edge Medical Centre,
Talbot Road,
Alderley Edge

016 2570 4080

Alderley Edge, Cheshire Opening Times

Mon 09:00 - 17:00
Tue 09:00 - 17:00
Wed 09:00 - 17:00
Thu 09:00 - 17:00
Fri 09:00 - 17:00
Sat Closed
Sun Closed
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