During your pregnancy, you will be offered 2 ultrasound scans. The first will take place between 11-14 weeks and is known as the dating scan. The second scan is around 18-21 weeks and is also known as the 20 week or anomaly scan.
If it is deemed medically necessary, early pregnancy scans may be offered and additional growth scans may be required after 23 weeks of pregnancy.
All scans undertaken at Rosie Ultrasound are performed by qualified sonographers. As the Rosie hospital is a teaching hospital, there may also be students present in the scan room. You also may be asked if a trainee sonographer can perform your scan. A qualified sonographer will always be present in these cases, however, you are allowed to decline being scanned by a trainee and this will not affect the care that is provided to you.
11-14 weeks Dating scan
The dating scan takes usually 20 minutes.
The purpose of the dating scan is to check:
- how many weeks pregnant you are and work out your due date (the estimated date of delivery, or EDD)
- whether you're expecting more than 1 baby
- that the baby is growing in the right place
- your baby's development
The combined screening test for Down’s, Edward’s and Patau’s, may also take place during this scan. The combined screening test involves measuring the fluid at the back of baby’s neck (nuchal translucency) during the scan, followed by a blood test.
Combined screening will be undertaken if:
- you have agreed to have screening for the conditions
- the scan takes place between 11 and 14 weeks of pregnancy when the crown rump length (CRL) measurement of the baby is between 45.0mm and 84.0mm.
The combined screening test will not be able to be performed if your dating scan happens after the baby’s CRL is more than 84mm, or if the CRL or nuchal translucency cannot be accurately measured. If this is the case, you will be offered another blood test (the ‘Quad’ test) at 16 weeks of pregnancy to screen for your chance of having a baby with Down’s syndrome. This test cannot screen for Edward’s or Patau’s and is not quite as accurate as the combined test.
The 20 week scan (Anomaly scan)
The anomaly scan usually takes 30 minutes.
This scan can take place between 18-21 weeks and is a detailed anatomy check of your baby. This screening scan is offered to everyone, however you do not have to have it if you do not wish.
The scan checks the physical development and growth of your baby. Sometimes serious health conditions may be picked up at this scan. However not every condition can be identified. The location of the placenta will also be checked at this scan. The sonographer may be able to give you an opinion on the sex of your baby at this scan, should you wish to know.
The 18-21 weeks screening scan is carried out in the same way as the 11-14 week scan. It produces 2D black and white images to give views of your baby. The NHS screening programme does not use colour or 3D images.
More information about the anomaly scan is available on the gov.uk website (opens in a new tab).
Early pregnancy
If there are medical concerns about the viability of your pregnancy, you may be offered a scan in early pregnancy. If you have any concerns during your pregnancy prior to your dating scan, please contact Clinic 24 for advice on 01223 217636 08:00-20:00 Monday-Friday and 08:00-14:00 Saturday/Sunday.
Growth Scans
Some women, who are following a high risk pathway, may be offered additional scans which will take place after 23 weeks of pregnancy. These scans assess your baby’s growth and wellbeing and may be used in conjunction with other tests and input from the obstetric team. Growth scans usually take 30 minutes.