Anatomy Scan At 23 Weeks | What Timing Really Means

A 23-week anatomy scan falls at the upper end of the standard 18–22 week window and is generally considered acceptable for a detailed fetal.

You probably heard the anatomy scan called the “20-week scan” and assumed it had to happen right at that mark. So when your appointment lands at 23 weeks, it’s natural to wonder if you’re missing the window.

The honest answer is that 23 weeks is the upper boundary of what many health systems still consider routine. While the ideal timing sits a week or two earlier, getting the scan at 23 weeks is common and usually provides all the information your care team needs.

Why 23 Weeks Feels Late But Isn’t

The standard anatomy scan window runs from 18 to 22 weeks, with most sources pointing to 20 weeks as the sweet spot. But the 23-week mark is explicitly included in the acceptable range by major health authorities. The NHS, for example, notes the scan can be done up until 23 weeks.

One reason earlier timing matters: if a significant structural issue is found, having more time allows for additional testing and decision-making. Some clinicians note that after 22 weeks, certain medical options may be more limited, though this varies by region and individual circumstances.

Another consideration is fetal viability. Cleveland Clinic explains that a baby born at 23 weeks may survive with intensive care. That doesn’t mean the scan is urgent the way a viability scan is, but it underscores that the fetus is far enough along for detailed imaging.

What The Scan Actually Looks For

By 23 weeks, most major organs are developed enough to be seen clearly on ultrasound. The sonographer checks a systematic list of structures, often using a “rule of three” approach — visualizing three anatomical landmarks in each plane. Here’s what’s typically examined:

• Brain and spine: The skull, brain structures (cerebellum, ventricles), and the spine are checked for defects like spina bifida or anencephaly.
• Heart: Four chambers are viewed, along with the outflow tracts, to identify serious cardiac abnormalities.
• Kidneys and bladder: The presence of both kidneys and a normal bladder is confirmed. Conditions such as bilateral renal agenesis can be ruled out.
• Abdominal wall: The stomach, diaphragm, and abdominal wall are examined for hernias like gastroschisis or exomphalos.
• Limbs and face: Arms, legs, hands, feet, and the upper lip are checked for cleft lip and palate or other limb anomalies.

The sonographer also measures the baby’s size — head circumference, abdominal circumference, and femur length — to confirm growth matches gestational age.

How The Scan Is Performed And Timed

The anatomy scan takes about 30 to 60 minutes, depending on the baby’s position and the amount of detail needed. You’ll lie on an exam table while a technologist glides a transducer over your belly, using gel to improve contact. The scan is non-invasive and carries no known risks to you or the baby.

If the baby is lying in a way that makes certain views difficult (spine or heart views are common culprits), you may be asked to walk around, drink water, or return on another day. A second attempt is normal and doesn’t indicate anything is wrong.

The NHS clearly states on its 20-week scan timing page that the scan is ideally performed before 21 weeks but can be done up to 23 weeks in some cases. For a baby positioned well, a 23-week scan still delivers reliable images.

If your scan is scheduled at 23 weeks, you’re still within the range where most ultrasound machines provide excellent detail. The window closes more for medical-legal reasons than for technical imaging limits.

What Happens If Something Shows Up

Most anatomy scans — around 95% — are normal, so the odds are in your favor. But it helps to know the process if a finding does arise:

1. Sonographer flags an area for review. The technologist notes an image that looks unusual and may consult a radiologist or maternal-fetal medicine specialist right away.
2. You’re offered a follow-up scan. If the view was unclear or a potential issue was spotted, a repeat scan in 1–2 weeks is common. Sometimes the baby simply moves into a better position.
3. You meet with a specialist. If a structural abnormality is confirmed, you’ll be referred to a maternal-fetal medicine doctor or a genetic counselor to discuss next steps.
4. Additional testing is discussed. This may include a detailed fetal echocardiogram, amniocentesis, or chromosomal microarray, depending on what was found.

Your care team will walk you through every option, including timing for any interventions or further monitoring. Many findings are minor and do not affect the baby’s long-term health.

Can A Scan Be Done After 23 Weeks?

Yes, but it becomes less typical. Some women have their anatomy scan later because they booked late, had scheduling conflicts, or needed a repeat scan after an earlier attempt was incomplete. In these cases, the scan is still valuable — it can check most structures, though some measurements (like nuchal fold or nasal bone) lose relevance after a certain point.

Healthline’s anatomy scan evaluation page explains that the scan evaluates the baby’s stomach, abdominal wall, diaphragm, and kidneys regardless of exact week. Even at 24 or 25 weeks, many of the same organ checks can be performed, though the window for certain early medical options may have passed.

If you’re past 23 weeks and haven’t had an anatomy scan, your provider will likely schedule it as soon as possible. It’s never too late to check on growth and anatomy, but the earlier the data, the more flexibility your team has.

The Bottom Line

A 23-week anatomy scan is still within the accepted range and will give you a thorough look at your baby’s development. If possible, earlier timing — between 18 and 22 weeks — is preferred to preserve options for follow-up, but a late scan is far better than no scan at all.

Your midwife or obstetrician can tell you whether your specific 23-week appointment fits within the guidelines for your care plan, and they’ll help you understand what to expect during the ultrasound.