Purpose of the Dating scan
The dating scan is commonly referred to as the ‘12 week scan’ but can be carried out approximately between 10-14 weeks of pregnancy. The scan itself lasts approximately 20 minutes. Ultrasound waves are used to carry out the scan and there are no known risks to you or the baby. It is optional and is offered for a number of reasons:
- To check the baby’s heartbeat
- To determine if you have a single or multiple pregnancies
- To measure the baby to estimate how many weeks pregnant you are and the due date
- To check for some conditions visible at this stage
- To offer combined screening for Down’s, Edward’s and Patau’s syndrome
Preparing for your Dating Scan
We ask for you to come for your dating scan with a full bladder. You should drink a pint of water approximately an hour before your appointment time.
Please also remove any belly button bars or rings as these may damage the ultrasound equipment.
You may bring a support person with you to the scan appointment who can come into the exam room with you. We ask you not to bring children to the hospital unless absolutely necessary. Your support person may be asked to wait outside with the child if this situation occurs.
Performing the Dating Scan
The scan will be performed in a dimly lit room and you will be asked to lie on a flat couch. You will be asked to move your trousers or skirt down onto your hips and tissue will be tucked in to protect your clothes. Clear (perhaps cold) ultrasound gel will then be applied and the sonographer will commence the exam.
To get optimum views of your baby, slight pressure may have to be applied. The sonographer will be concentrating and it may take some time before the screen is turned to show you the baby, this is normal. The sonographer may be quiet throughout the scan, again, this is normal.
To get good-quality images it may be necessary for you to get up, move your hips or empty your bladder. In some cases, you could be asked to go for a walk and return for a second attempt.
Sometimes due to a number of factors an abdominal scan may not be sufficient and you will be offered a transvaginal scan. This would involve a long thin probe with a latex-free cover being inserted into the vagina for a clearer view. This does not hurt and will not harm the baby.
What measurements/anatomy checks are included
- A Crown to Rump Length (CRL) is taken of your baby; this is from the top of the head to the bottom (not including the legs). This measurement is used to determine exactly how many weeks pregnant you are and your estimated date of delivery (due date). If you have had IVF your due date will not change based on this measurement however a CRL may be taken if you opt to have the combined screening
- The baby’s bladder will be observed
- The baby’s skull and brain will be observed
- The baby’s abdomen including the insertion of the cord will be observed
- Your ovaries and adnexa (adjoining parts e.g., fallopian tubes and ligaments) will be observed
- If you decide to have combined screening a measurement of Nuchal Translucency (NT) will also be taken (see below)
This is an optional screening test offered to everyone at the Dating Scan, the sonographer will ask you if you fully understand and if you consent to have it. The test determines the chance of your baby having Down’s syndrome, Edward’s syndrome or Patau’s syndrome. If you choose to have this test a measurement at the back of the baby’s neck called the Nuchal Translucency (NT) will be taken during the scan and a blood test will be taken afterwards. The sonographer will be able to tell you if the NT is within normal range but you require the blood test for a full result.
The result of this test comes back as a 1 in a numerical chance of your baby having one of these conditions. Anything less than 1 in 150 is classified as a high chance result, you would be contacted by the screening team and offered a Non Invasive Prenatal Screening Test (NIPT) and/or referral to fetal medicine.
More information can be found on these conditions and the test in the ‘Screening for Down’s syndrome, Edwards’ syndrome and Patau’s syndrome’ leaflet. This can be found online or on your BadgerNotes portal.
Other things to note
No money is currently being taken for scan photos due to Covid 19, instead, two scan photos will be printed for you for free.
Video equipment is not to be used under any circumstances in the scan room. We ask that all phones are turned off for the duration of the exam.
It is not possible to determine your baby’s sex at the Dating Scan, the baby is too small at this stage.
If when you are scanned the baby is too small for these anatomy checks you may have to return on another day for another appointment.
If when you are scanned the baby is larger than expected a head circumference measurement will be taken and combined screening may not be possible.
Combined Screening may also not be possible after two attempts due to the baby lying in an awkward position or if you are above average weight. In these cases the options would be:
- The quadruple test which is just for Down’s syndrome can be offered between 14 and 20 weeks
- No screening, although Edward’s and Patau’s syndromes are screened for at the anomaly (20 week) scan
At the end of your scan the sonographer will inform you if everything appears normal. It may be necessary to get a second person to scan you if anything is unclear.
A more detailed view of the baby’s anatomy can be seen and will be examined at your anomaly scan should you choose to have it.
Your scan report should be uploaded to your BadgerNotes a few hours after your appointment.
Useful sources of informationScreening in pregnancy 12 week scan Screening for Down’s syndrome, Edwards’ syndrome and Patau’s syndrome Screening tests for you and your baby
If you have additional queries, particularly regarding the appointment time please contact:
Women’s Health Clinic
Or any other pregnancy questions please contact:
Pregnancy Assessment Unit
Any personal information is kept confidential. There may be occasions where your information needs to be shared with other care professionals to ensure you receive the best care possible.
In order to assist us to improve the services available, your information may be used for clinical audit, research, teaching and anonymised for National NHS Reviews and Statistics.
This leaflet can be made available in other languages and formats upon request