Pregnancy scans explained: dating, NT and anomaly scans
Most women have at least two scans: a dating scan at 8 to 14 weeks to confirm the due date and how many babies, and an anomaly scan at 18 to 21 weeks to check how the baby is developing. Many also have a nuchal translucency (NT) scan at 11 to 14 weeks for screening, and growth scans later if needed. Ultrasound uses sound waves, not radiation, and is considered safe.
Key facts
| Early scan | 6 to 10 weeks, if you have bleeding or pain, or after IVF |
|---|---|
| Dating scan | 8 to 14 weeks |
| NT scan | 11 to 14 weeks |
| Anomaly scan | 18 to 21 weeks |
| Radiation | None: ultrasound uses sound waves |
How ultrasound works
Scan by scan
| Scan | When | What it checks |
|---|---|---|
| Early (viability) | 6 to 10 weeks | Pregnancy in the womb, heartbeat. Often done internally. |
| Dating | 8 to 14 weeks | Due date, number of babies, early development |
| Nuchal translucency (NT) | 11 to 14 weeks | Fluid at the back of the neck, combined with blood tests to screen for Down's syndrome and other conditions |
| Anomaly | 18 to 21 weeks | Baby's organs, spine, heart, face and limbs; placenta position |
| Growth | 28 weeks onwards, if needed | Size, fluid, blood flow (Doppler) |
See what's due now with the scans and tests timeline.
How to prepare
- Early abdominal scans may need a full bladder. Drink water an hour before.
- Wear loose clothes that make it easy to uncover your tummy.
- Bring your hospital file and a list of questions.
Screening and diagnostic tests
Screening tells you the chance of a condition. The combined test (NT scan plus blood test) is offered in many countries. NIPT (cell-free DNA) is a blood test from about 10 weeks that is more accurate for Down's syndrome. If screening shows a higher chance, diagnostic tests such as CVS (11 to 14 weeks) or amniocentesis (from 15 weeks) can give a definite answer, with a small risk of miscarriage.
3D and 4D scans
These give lovely keepsake pictures but aren't a medical check. Choose a qualified provider and keep them short. You can also watch our 3D baby animation.
Can a scan show the sex?
Often at the anomaly scan, where law and hospital policy allow. Read boy or girl: when can you find out?
Frequently asked questions
Are ultrasound scans safe?
Why might my due date change after the scan?
What if the scan finds a problem?
Sources
- NHS: Ultrasound scans in pregnancy
- ISUOG Practice Guidelines: routine mid-trimester scan
- ACOG Practice Bulletin 226: Screening for fetal chromosomal abnormalities
General information, not medical advice. Medical disclaimer · How we review content
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