12-Week and 20-Week Scans: What to Expect on the NHS

Most people in England have two routine ultrasound scans during pregnancy. You may be offered more if you are expecting twins or your maternity team wants to check something.

When are the NHS pregnancy scans?

Your maternity service books both. If you have not heard about a dating scan by around 12 weeks, contact your midwife.

What happens at the 12-week scan?

The dating scan works out how many weeks pregnant you are and your due date. It also checks whether you are expecting more than one baby, that the baby is growing in the right place, and your baby's development. You may be asked to arrive with a full bladder, because it makes the ultrasound image clearer.

Your due date from this scan usually replaces the date worked out from your last period. You can compare the two with our due date calculator.

What is the combined screening test?

If you choose to be screened for Down's syndrome, Edwards' syndrome and Patau's syndrome, it can happen at the dating scan. The combined test uses a blood test and an ultrasound measurement of the fluid at the back of the baby's neck (nuchal translucency). It has to be done when you are between 10 and 14 weeks.

Screening gives a chance, not a diagnosis. If your result shows a higher chance, you can choose a more accurate screening blood test called NIPT, or a diagnostic test (chorionic villus sampling or amniocentesis) that can tell you whether your baby has the condition. If you are past 14 weeks, you may be offered the quadruple blood test between 14 and 20 weeks instead; it checks for Down's syndrome but is not as accurate as the combined test.

Screening is offered to everyone who is pregnant, and it is your choice whether to have it. You can also choose which conditions to be screened for.

What does the 20-week scan check for?

The 20-week scan looks at your baby's bones, heart, brain, spinal cord, face, kidneys and abdomen. It screens for 11 conditions:

1. Anencephaly
2. Open spina bifida
3. Cleft lip and palate
4. Diaphragmatic hernia
5. Gastroschisis
6. Exomphalos
7. Serious cardiac abnormalities
8. Bilateral renal agenesis
9. Severe skeletal dysplasia
10. Edwards' syndrome
11. Patau's syndrome

The scan cannot find every condition, so a clear result is reassuring but not a guarantee.

Can I find out the sex at the 20-week scan?

You may be asked whether you would like to know the sex. It is not always possible to tell, depending on the baby's position, and some hospitals have their own policy, so ask the sonographer at the start of the scan.

Can my partner come to the scan, and can I get photos?

Partners can usually attend, but most hospitals do not allow children. Check with your hospital or clinic before the appointment whether you need to pay for pictures.

What happens if the scan finds something?

The sonographer may ask a colleague for a second opinion. You may be offered more scans or tests, such as amniocentesis or chorionic villus sampling, and referral to a specialist. You can take time to decide what you want to do and ask for support. Our antenatal anxiety guide covers where to find help if waiting for results feels overwhelming.