The Short Answer
The first routine ultrasound — called the dating scan or first trimester scan — is typically performed between 8 and 14 weeks of pregnancy, most commonly around 11–13 weeks. This scan confirms the pregnancy, establishes gestational age, and screens for chromosomal conditions.
Types of First Ultrasound Scans
Dating Scan (8–14 Weeks)
The most common first scan. Its main purposes are to:
- Confirm the pregnancy is in the uterus (not ectopic)
- Measure the embryo or foetus to estimate a due date
- Check for a heartbeat
- Confirm the number of embryos (identify twins or multiples)
Early Viability Scan (6–8 Weeks)
Offered when there is bleeding, pain, or a history of miscarriage. At 6 weeks, a heartbeat may be visible — a strong indicator of a viable pregnancy. This scan is usually transvaginal.
Nuchal Translucency Scan (11–14 Weeks)
Often performed alongside the dating scan. Measures fluid at the back of the baby's neck (nuchal translucency) as part of combined screening for Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and Patau syndrome (trisomy 13). Results are combined with blood tests (PAPP-A and free beta-hCG) for a risk estimate.
What the First Ultrasound Checks
- Heartbeat: Visible from around 6 weeks; strongly reassuring at 8–10 weeks (150–180 bpm is normal)
- Crown-rump length (CRL): Measurement from head to tailbone to calculate gestational age and due date
- Number of embryos: Identifies twins, triplets, or more
- Location: Confirms intrauterine pregnancy (rules out ectopic pregnancy)
- Placenta position: Early assessment
- Uterus and ovaries: Checks for fibroids, ovarian cysts, or other issues
What to Expect During the Scan
- Duration: 15–30 minutes
- Transabdominal scan: Gel on the abdomen, probe moved gently across the skin. A full bladder helps image quality in early pregnancy (many clinics ask you to drink water beforehand).
- Transvaginal scan: A small probe is gently inserted for clearer images, especially before 10 weeks when the uterus is still low in the pelvis. This is safe and normal.
Most scans produce still images or short video clips that you can take home.
How Accurate Is the Dating Scan?
A dating scan performed at 11–13 weeks is accurate to within ±5 days for estimating gestational age, according to the Society of Obstetricians and Gynaecologists of Canada (SOGC). This is more accurate than period-based calculations, especially for women with irregular cycles.
When Should You Book?
Most guidelines recommend booking your first antenatal appointment (booking appointment) at 8–10 weeks, so the dating scan can be scheduled in time for combined first-trimester screening at 11–13 weeks.
If you are unsure of your dates, are experiencing pain or bleeding, or have had a previous ectopic pregnancy or miscarriage, ask your provider about an earlier viability scan.
Country-Specific Schedules
| Country | Routine First Scan |
|---|---|
| UK (NHS) | 8–14 weeks (dating scan) |
| USA | Variable; often 10–13 weeks |
| Australia | 11–13 weeks (dating + NT scan) |
| Norway | 17–19 weeks (standard); 11–14 weeks on request |