By Sarina Gomez
This article is general information, not medical advice. Ask your midwife, OB-GYN or sonographer about your own pregnancy and scans.
A 12 or 13 week sonogram dates your pregnancy, counts how many babies there are and checks the heartbeat. If you chose screening, it also measures the fluid at the back of the baby’s neck. On the screen you’ll see a small, curled-up baby in black and white, usually with a clear side profile, a big head, tiny arms and legs, and plenty of wriggling. Faces, hair and “who does the baby look like” come much later.
What the 12 week scan checks
The scan at the end of the first trimester has a few clear jobs. The NHS offers it at around 10 to 14 weeks and lists them as working out your due date, checking whether you’re expecting more than one baby, checking that the baby is growing in the right place, and looking at early development. ACOG gives a similar list for a first-trimester ultrasound in the US: estimating gestational age, helping screen for certain genetic disorders, counting babies, checking the heart rate and checking for an ectopic pregnancy.
The names differ by country, which confuses a lot of people:
| Where | What it’s usually called | Timing |
|---|---|---|
| UK (NHS) | Dating scan, “12 week scan” | about 10 to 14 weeks |
| US | First-trimester ultrasound, NT scan | about 10 to 13 weeks for NT screening |
One difference matters. In the US a first-trimester scan isn’t standard for everyone. ACOG notes it’s “too early to see many of the fetus’s limbs and organs in detail”, and the one standard exam is usually done at 18 to 22 weeks (more on that in our 20 week anatomy scan guide).
The nuchal translucency measurement
The NT measurement is a screening step, not a diagnosis. According to ACOG’s guide to prenatal screening, first-trimester screening pairs a blood test with an ultrasound measurement of “a space at the back of the fetus’s neck”, usually between 10 and 13 weeks. The NHS calls this pairing the combined test.
A result comes back as a level of risk. ACOG is clear that a positive screening result means a higher chance compared with the general population, “it does not mean that your fetus definitely has the disorder.” Only diagnostic tests such as CVS or amniocentesis give a more definite answer. If you get a result you don’t understand, your provider is the person to ask, not a forum.
What a 13 week sonogram picture shows
A 13 week sonogram picture shows the outline of your baby, not their features. The image is built from echoes: dense tissue such as bone sends back a strong echo and shows up white, while fluid sends back almost nothing and shows up black. That’s why the skull and spine often look bright and the fluid around the baby looks like a dark pool.
Here’s what you can usually pick out, if the baby is lying well:
- The profile. The forehead, the bridge of the nose and the chin, side-on. This is the view most parents want printed.
- The head. It looks large next to the body. That’s normal at this stage.
- Arms and legs. Often bent, sometimes waving. You might catch a hand near the face.
- Movement. On the live screen, babies at this age can be surprisingly busy, even though you won’t feel it yet.
What you won’t see is a face you could recognize. ACOG’s week-by-week guide says eyelids have formed but stay closed during weeks 9 to 12, and the skin during weeks 13 to 16 is still thin. Ears, nose and lips only become recognizable on ultrasound at around 17 to 20 weeks. For a stage-by-stage look, see ultrasound pictures by week.
How to prepare for the scan
Preparation is simple, and it mostly comes down to your bladder. The NHS says you may need a full bladder because it makes the image clearer. ACOG describes the same thing for a scan over the belly: you may need to drink several glasses of water in the 2 hours before, so the full bladder acts as a “window”. Early scans are sometimes done with a vaginal probe instead, and then you’ll be asked to empty your bladder first. Call ahead and ask which one you’re having.
A few practical things help:
- Wear a two-piece outfit so you only need to lift your top.
- Plan for about 20 minutes. That’s the NHS estimate for the dating scan.
- Bring your questions written down. Good ones: “What’s the crown-rump length, and does it change my due date?”, “Can you show me the profile?”, and “Can I have a printed or digital copy of the side view?”
- Ask about pictures before you go. Some clinics charge for prints, others send a digital copy.
Can you tell the sex at 12 or 13 weeks?
Usually not reliably from the picture. ACOG notes that the genitals only begin to form in weeks 9 to 12, and its standard exam at 18 to 22 weeks says the sex may be visible “if the fetus is in a good position”. That’s why the internet’s favorite 12-week trick, the nub theory, is a guessing game rather than a result.
Blood screening is a different route. ACOG says cell-free DNA screening can be done from 10 weeks and looks at sex chromosomes, among other things. Ask your provider whether the sex can be included in your report and how reliable it is for you. Our guide on when you can find out the gender lays out every method by week.
Making more of your 12 week picture
A 12 week picture is a lovely keepsake, but it’s a long way from a face. If you’d like to imagine one anyway, SeeMyBaby turns a photo of your scan into an imagined newborn portrait in about a minute. Be realistic about what that means at 12 or 13 weeks: a grainy 2D side view gives the app very little to work with, so the result leans heavily on imagination. It’s a playful picture, not a forecast, and a clear 3D scan later in pregnancy gives a much closer starting point.
If you’re planning to share the news around this scan, our ultrasound announcement ideas are built around the scan photo itself, and the blog has more guides for every stage of the scans.
What the scan can’t tell you
No ultrasound finds everything, and a first-trimester scan sees the least detail. RadiologyInfo, written by radiologists, states plainly that obstetric ultrasound “cannot identify all fetal abnormalities.” The 12 week scan is a first check. The detailed look at the brain, heart, spine, face and limbs happens at the anatomy scan around 18 to 22 weeks.
On safety, ACOG says there is currently no evidence that ultrasound harms a developing baby, and recommends that scans be done only for medical reasons by qualified professionals. That’s worth knowing if you’re tempted by extra scans just for pictures.
Sources
- ACOG: Ultrasound Exams
- ACOG: Prenatal Genetic Screening Tests
- ACOG: How Your Fetus Grows During Pregnancy
- NHS: 12-week scan
- RadiologyInfo (ACR/RSNA): Obstetric Ultrasound
Questions parents ask
Is the 12 week scan the same as the NT scan?
Often it’s the same appointment. If you’ve opted into screening, the nuchal translucency measurement is taken during the scan, usually between 10 and 13 weeks according to ACOG.
Do I need a full bladder for a 13 week ultrasound?
Often, yes, for a scan over the belly, because a full bladder makes the picture clearer. Ask the clinic when you book, since an early vaginal scan needs an empty bladder instead.
Can you see the baby’s face at 13 weeks?
You’ll see the profile outline: forehead, nose bridge and chin. ACOG notes that ears, nose and lips only become recognizable on ultrasound at around 17 to 20 weeks.
How long does the 12 week scan take?
The NHS says the dating scan usually takes about 20 minutes. It can take longer if the baby isn’t lying in a helpful position.
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