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 3D ultrasound collects many thin 2D slices of your baby and uses software to turn them into a shaded, three-dimensional surface, which is why you can see cheeks, lips and tiny fingers instead of a gray cross-section. In medical care it’s a specialized tool used when a doctor needs a closer look; most routine pregnancy scans are 2D. Keepsake 3D scans are elective, and the FDA, ACOG and the AIUM all discourage ultrasound done only to get pictures.
How a 3D ultrasound picture is made
A 3D image starts the same way as any ultrasound: with sound and echoes. As ACOG explains, a transducer sends sound waves into the body, the waves bounce off tissue, fluid and bone, and the returning echoes are turned into images.
What changes in 3D is the processing:
- The probe sweeps a volume. Instead of one slice, the machine records a stack of slices across the area of interest.
- Software finds the surface. It looks for the boundary between amniotic fluid (which returns few echoes and looks dark) and the baby’s skin (which returns many).
- The surface is shaded. A virtual light source adds highlights and shadows so the result reads as a face. The amber or skin-like tint is a display setting chosen on the machine; it says nothing about your baby’s skin tone.
That last step is why fluid matters so much. The software needs a pocket of fluid in front of the face to “see” the skin. If the face is pressed against the placenta, the uterine wall or a hand, the surfaces merge and the picture smudges.
What a 3D ultrasound can and can’t show
| Usually shows well | Often hidden or misleading |
|---|---|
| The shape of the cheeks, nose, lips and chin | True skin color (the tint is software) |
| Hands, fingers, feet and toes | Eye color, since eyelids stay closed until late pregnancy |
| Expressions like yawns or a pout | Hair, which is fine and close to the scalp |
| The baby’s position | Features covered by a hand, cord or placenta |
According to MedlinePlus, a baby’s eyelids close around weeks 11 to 14 and don’t reopen until about week 28, so even a great 3D picture won’t show eye color.
3D versus your routine 2D scans
Your medical scans are mostly 2D, and that’s by design. Cleveland Clinic describes 2D as the most common type, 3D as adding depth and angles, and 4D as “3D ultrasound in motion”. ACOG recommends at least one standard exam, usually at 18 to 22 weeks, and lists 3D among the specialized techniques used when a problem is suspected. RadiologyInfo notes that some physicians also use 3D to check how the baby is developing.
In practice that means a 3D picture from your hospital is a bonus, not a given. Keepsake studios, by contrast, offer 3D and 4D as the main event. Our side-by-side of 3D vs 4D ultrasound compares what each format gives you to take home.
When to book a 3D ultrasound
Timing changes the face more than anything else. Around weeks 17 to 20, ACOG notes that the ears, nose and lips become recognizable on an ultrasound. Fat starts forming under the skin at about 21 to 24 weeks, and between 25 and 28 weeks the skin begins to look smoother as more fat is added.
So a 3D face at 20 weeks often looks thin and bony, while a face in the late second or early third trimester looks rounder and more like a newborn. Later still, there’s less fluid in front of the face and the baby may have dropped lower, which can make a clear view harder. Our week-by-week guide to the best time for a 3D ultrasound goes through each stage, and how to get clear 3D ultrasound pictures covers what you can and can’t control on the day.
Is a 3D ultrasound safe?
There’s no evidence that ultrasound harms a baby, but experts still advise against scanning only for pictures. Here is where the main US bodies stand:
- ACOG: “There is no evidence that ultrasound is harmful to a developing fetus,” but because effects could be identified in the future, exams should be done “only for medical reasons by qualified health care professionals,” and casual use should be avoided (ACOG).
- FDA: Ultrasound can heat tissue slightly and can sometimes create small gas pockets (cavitation); “the long-term consequences of these effects are still unknown.” Using ultrasound only for keepsake videos is discouraged, though keepsake images are reasonable if they come from a medically indicated exam with no extra exposure (FDA).
- AIUM: It “strongly discourages the nonmedical use of ultrasound,” and encourages sharing images with patients during medically indicated scans (AIUM).
What that means for you: the lowest-exposure way to get a keepsake is to ask for a picture at a scan you’re already having. If you still choose a studio, ask who does the scan and what training they have, how long the session lasts, and whether the images go to your OB-GYN or midwife. Our guide to 3D ultrasound safety turns these positions into a full list of questions.
From a 3D scan to an imagined newborn
A 3D picture still isn’t the face you’ll meet. Newborns look different from their scans for reasons we cover in 3D ultrasound vs a real baby. If you’d like to imagine the face from the picture you already have, SeeMyBaby turns one scan photo into an imagined newborn portrait in about a minute. It’s for fun, not a prediction: the app doesn’t analyse the scan medically, and a clear 3D profile gives a closer result than a blurry one.
Sources
- American College of Obstetricians and Gynecologists: Ultrasound Exams and How Your Fetus Grows During Pregnancy
- U.S. Food and Drug Administration: Ultrasound Imaging
- American Institute of Ultrasound in Medicine: Prudent Use and Safety of Diagnostic Ultrasound in Pregnancy
- Cleveland Clinic: Ultrasound
- RadiologyInfo (ACR/RSNA): Obstetric Ultrasound
- MedlinePlus: Fetal development
- Odeh M, et al. Sonographic fetal sex determination. Obstet Gynecol Surv. 2009.
More scan guides are on the SeeMyBaby blog.
Questions parents ask
What is the difference between 3D and 4D ultrasound?
A 4D ultrasound is a 3D ultrasound shown in motion, so you see the baby move in real time. Our 4D ultrasound guide explains what to expect from the video.
Can you tell the sex on a 3D ultrasound?
The sex is normally checked on 2D images. A 2009 review in Obstetrical & Gynecological Survey described 3D as of generally limited value for sex determination.
Why does my baby look orange or gold on a 3D scan?
The color is a display setting that makes the surface easier to read. It isn’t your baby’s skin tone.
How many weeks is best for a 3D ultrasound?
The face usually looks fuller in the late second and early third trimester, after fat starts to form under the skin. Our best time for a 3D ultrasound guide has the week-by-week detail.
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