12 week pregnancy dating scan: What do I need to know?

It's your first pregnancy ultrasound where you see your baby for the first time, but what's it all about?

Your 12-week pregnancy dating scan

You won’t have known that you’re pregnant long, but your 12 week dating scan offers an exciting opportunity to see your little one developing in the womb and give you an idea of your estimated due date (EDD).

12 week scan

Will the dating scan happen at exactly 12 weeks? 

You should have your first pregnancy ultrasound scan in between 10 weeks and 13 weeks pregnant, but it can vary on a couple of other factors including where you live and how you’ve been up to the 12th week of pregnancy

If there’s any cause for concern then you may be recommended to have the scan before the 12-week mark, and your midwife will be able to assist you with this. 

The nuchal translucency scan is usually done at the same time and done in conjunction with a blood test.

Where do I go for my 12-week scan? 

Your scan will be booked for you by your doctor or midwife and will usually take place at your local hospital’s ultrasound department. The scan will be carried out by a sonographer, who is trained in performing scans and knowing what to look out for. 

Your sonographer will be able to answer any questions you have on the day and will talk you through the process. 

What will the dating scan involve? 

Before you go for your scan, you’ll be asked to drink lots of water and arrive with a full bladder. This can be a bit uncomfortable if you have to wait with a full bladder but it does put your uterus in a better position for scanning.

The dating scan is non-intrusive and won’t be painful; in fact, it can be quite a relaxing and exciting experience to see your little one and their tiny heartbeat for the first time. 

The process will involve lying back on a bed, with gel applied to your belly. The sonographer will then use a transducer device which uses ultrasound to produce an image of your baby inside the womb to a small display screen next to you. The scan will usually last for around 20 minutes. 

What will I find out at the 12-week scan? 

The dating scan is the first time you (or anyone) will have seen your baby so there’s a few things that your sonographer will look out for and things you’ll find out: 

• How many weeks pregnant you are, and your EDD (estimated date of delivery). This will be a lot more accurate than working it out just using the date of your last period. 

• Find out if the baby is growing in the right place
• Find out if you’re expecting twins, triplets or more! 
• Check your baby’s general development including their heartbeat, limbs and some organs 
• Other potential abnormalities including spinal bifida 
• Most hospitals will be able to sell you a copy of your scan photo for a few pounds or ask for a donation

Can I have a screening test at my dating scan? 

Most units will offer you a screening test at the same time. Screening tests for Down’s Syndrome is best performed after the dating scan as an accurate due date is required to assess whether hormone levels are actually abnormal or normal for that stage of pregnancy. 

The combined results of this test combined with a nuchal translucency scan will be used to calculate the chance of your baby developing Down’s Syndrome. 

If you haven’t had the combined nuchal scan and blood testing for screening for chromosome abnormalities, you’ll be offered a screening blood test between 14 and 20 weeks. 

In around 3 to 5% of pregnancies, results are classified as higher risk, but most of those women will still go on to have healthy babies.

Why have the tests if they’re not always accurate?

It can be frustrating and worrying if you’re not given a definite answer, but it is important to have a fast and effective way of screening for potential problems without putting baby at any risk.

The diagnostic tests that give a definitive yes or no can carry a small risk of miscarriage because it involves removing a tissue or fluid from inside the womb for testing.

If screening tests show a lower risk, most parents choose not to put themselves, or their unborn baby through further, more invasive tests.

12 week pregnancy dating scan: What do I need to know?