12 week scan: Your dating scan guide
If you’re waiting until your first scan to share your news, you might feel like 12 weeks can’t come soon enough. Learn why the dating scan is carried out and get tips to help you prepare for your appointment.
Your baby, this week
Discover the science behind your baby's developments, week-by-week
The 12-week scan or dating scan
Although sometimes known as the reassurance and viability scan, your 12 week scan is more typically referred to as the dating scan. Bear in mind that you may not have your scan at exactly 12 weeks; it usually takes place between your 10th and 14th week of pregnancy1.
During the first scan your sonographer will check the size of your baby to give a more accurate idea how many weeks you’ve been pregnant and your due date. It will provide clarity on whether you are expecting more than one baby and the scan will also determine the ‘viability’ of the pregnancy by confirming that the baby is growing as expected within the womb and developing correctly. The scan is harmless to mother and baby and will typically take 20 to 30 minutes for the sonographer to complete before he or she provides a report for your midwife to share with you.
The nuchal scan
As part of your first scan at around 12 weeks, you may choose to have the Nuchal Transluceny (NT) scan which is part of the combined screening test for Down's syndrome2. The NT scan measures the nuchal fluid at the back of your baby’s neck1 because babies with Down’s syndrome may have an increased NT. It’s non-invasive and simply a case of the sonographer getting a good enough view of your baby’s neck to take a measurement on screen.
Sadly, for some the scan reveals that their baby isn’t developing as it should, or a heartbeat cannot be found, indicating an early miscarriage. It is an incredibly sad and difficult experience for any woman and her partner to go through, but help and support is available from charities such as miscarriageassociation.org.uk and tommys.org.
At 12 weeks pregnant, your baby is around 5-6cm in length3, with vital organs, bones and muscles in place, ready to grow and mature over the coming months.
- You may need to have a full bladder for your scan as it will improve the clarity of the ultrasound imaging by pushing the position of the uterus forward to the surface , you can ask your midwife or healthcare professional.
- Wear comfy clothes you can easily undo. A top you can pull up and loose trousers you can pull down will mean you don’t have to get undressed. The gel used can be messy, so wear something washable.
- You will be allowed to bring one person with you into the scanning room but check with your hospital before your appointment.
- Take some change in case you want to buy scan photos.
Oriana Hernandez Carrion
Oriana has a BSc (Hons) in Nutrition and Food Science (1st class) from University Iberoamericana in Mexico, the country where she completed an internship in a Children’s Public Hospital (HIMFG) and later on worked in a private nutrition clinic.
- NHS. 12-week scan [Online] 2020. Available at https://www.nhs.uk/pregnancy/your-pregnancy-care/12-week-scan/ [Accessed July 2021]
- NHS. Ultrasound scans in pregnancy [Online] 2020. Available at https://www.nhs.uk/pregnancy/your-pregnancy-care/ultrasound-scans/ [Accessed July 2021]
- NHS. Week-by-week guide to pregnancy [Online] 2021. Available at https://www.nhs.uk/start4life/pregnancy/week-by-week/1st-trimester/week-12/ [Accessed July 2021]
Last reviewed: 28th July 2021
Reviewed by Oriana Hernandez Carrion
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