Ultrasound scans in pregnancy
The dating scan and the anomaly scan: when they happen, what they check, what they feel like and whether they are safe.
3 min read
In this article
Most pregnancies have at least two main scans: the first between weeks 11 and 14, and the anomaly scan between weeks 18 and 21. Ultrasound is painless and has no known risks for you or your baby.
The dating scan (weeks 11 to 14)
This scan:
- measures your baby and dates the pregnancy more accurately, which may move your due date slightly from the one worked out from your last period
- shows whether you are expecting more than one baby
- can include a nuchal translucency measurement, part of screening for Down’s syndrome, if you choose it
For an early scan, you are sometimes asked to come with a full bladder. Ask the clinic beforehand.
The anomaly scan (weeks 18 to 21)
This is the most detailed scan. It looks carefully at how your baby is developing, including the heart, brain, spine, kidneys, face and limbs. It also checks where the placenta is and how your baby is growing.
If the placenta is low, you will have another scan later. The placenta often moves up by itself as your womb grows.
What happens
You lie on your back with your tummy uncovered. Gel is put on your skin and a probe is moved over your tummy, sometimes with a little pressure. It usually takes 20 to 30 minutes. It may take longer, or be repeated another day, if your baby is lying in a position that makes it hard to get good views.
Your baby’s sex
The sex can often be seen at the anomaly scan. Whether or not you want to know, say so at the start of the scan. The sonographer cannot be 100% sure, especially if your baby is turned away.
What a scan cannot show
A scan cannot pick up every health condition. If something worries you, talk to your doctor even if the scan was normal.
If a scan shows your baby may be more likely to have a condition, you may be offered more tests or a specialist’s opinion. Some tests, such as amniocentesis, carry a small risk of miscarriage, so the decision to have them is yours, once you have talked it through with your doctor.
If you are expecting more than one baby, have a long-term condition or have problems in pregnancy, you may have more scans. See also the schedule of pregnancy appointments.
Common questions
Are ultrasound scans safe in pregnancy?
When is the anomaly scan?
When can I find out the sex?
How long does a scan take?
Sources we consulted
Written by the mam.al editors as general information. It does not replace advice from your doctor or midwife. Contains public sector information licensed under the Open Government Licence v3.0.