What to Expect at Your 20 Week Anatomy Scan

Medically reviewed by Dr. Melissa Dennis, MD, MHA, FACOG

Halfway through pregnancy, one of the biggest milestones is the 20 week anatomy scan. Often called the anomaly scan, this detailed ultrasound gives you and your care team an in-depth look at how your baby is developing. It can be exciting, nerve-wracking, and filled with questions, especially if it's your first time.

Here’s what you need to know before heading into your 20 week ultrasound, what your provider is looking for, and how to prepare emotionally and practically.

What is the 20 week anatomy scan?

The anatomy scan is a comprehensive ultrasound done when you're around 20 weeks pregnant (usually between 18 and 22 weeks). The scan lasts about 45 minutes to an hour and is typically performed by a sonographer or ultrasound technician.

This is not just a quick look at the baby: it’s a detailed check of your baby’s organs, limbs, and overall development. The goal is to identify any structural concerns early and ensure that your baby developing on track. If anything looks unclear or needs a closer look, you may be referred to maternal fetal medicine (MFM) for follow-up. And while this scan is thorough, anomalies can be missed. 

What does the anatomy scan look for?

The anatomy scan checks all major systems from head to toe including:

• Brain and skull: The sonographer will look at the shape of the skull and major structures of the brain. They check for normal brain symmetry, fluid levels in the ventricles, and the presence of key landmarks like the cerebellum and corpus callosum.
• Face: Your provider will check the facial bones to rule out conditions like cleft lip or cleft palate, which can sometimes be seen on ultrasound. You might even catch a glimpse of your baby’s profile or sweet little nose and lips.
• Spine and limbs: Your provider will look to ensure the spine is fully formed, and that arms, legs, hands, and feet are all present and moving normally. Measurements are taken of the femur and humerus to assess growth and gestational age.
• Heart: The heart is a major focus of the anatomy scan. Your provider will confirm there are four chambers, check blood flow through the valves and major vessels, measure the heart rate and look for structural concerns like holes in the heart or abnormal positioning. If anything is hard to see or unclear (which can happen depending on baby’s position), you might be referred for a fetal echocardiogram or a consult with maternal fetal medicine.
• All major internal organs: Your provider will assess your baby’s development across major internal organs, including:
  
  • Lungs: The sonographer is looking for symmetry, size, and congenital anomalies in the developing lungs.
  • Stomach: When the stomach is filled with fluid, the scan confirms the baby is swallowing.
  • Bladder and kidneys: Seeing fluid in the bladder and both kidneys on the scan confirms that the baby is producing and passing urine.
  • Liver and intestines: The scan checks that the liver and intestines are in the correct position within the abdomen. It also looks for normal structure and development at the 20 week stage.
• Umbilical cord: Your provider will confirm that the umbilical cord has three vessels (two arteries and one vein), and that it is connected properly to your baby and the placenta. In the event of an abnormality,your provider will talk you through what it means.
• Placental location: Your provider will assess where the placenta is attached, whether it is covering the cervix (which would be called placenta previa), and how well it is supplying blood to the baby. Placental position can change as your uterus grows, so if it is low-lying now, it might resolve on its own by the third trimester.
• Amniotic fluid levels: Your provider will measure the amount of amniotic fluid around your baby. Too little fluid (oligohydramnios) or too much fluid (polyhydramnios) could be a sign of an issue, but mild variations are often nothing to worry about.
• Sex: if you want to know! The 20 week scan will confirm the results of earlier optional blood testing.

Your provider will also confirm or adjust your due date based on growth markers including baby’s head circumference, abdominal circumference, and femur length.

How common is bad news at the 20 week scan?

Most 20 week anatomy scans bring reassurance. Serious issues are rare, and many findings that do come up are minor or resolve on their own.

Still, it’s normal to feel anxious. Around 3–5% of scans may identify something that requires follow-up. These might include findings like a soft marker (like a choroid plexus cyst) or a minor kidney finding that often corrects with time. In more serious cases, like suspected heart defects or cleft lip, your care team will walk you through next steps, which may involve a maternal fetal medicine consult or additional testing.

Try to remember: more information doesn’t always mean something is wrong. It helps your care team give the best support possible.

How to prepare for your 20 week anatomy scan

You don’t need to do much to prep, but here are a few tips to make the experience smoother:

• Hydrate well the day before. Clear images rely on a full bladder and good fluid levels.
• Wear comfortable clothes. You’ll be lying on a table for a while.
• Bring your partner or support person if you can. The anatomy scan can be an emotional moment, and it can be helpful to have someone else there to take notes
• Ask if photos or videos are allowed, since clinics have different policies about recording during scans

You might also want to eat a light snack about 30 minutes beforehand. Sometimes a little sugar can help get the baby moving into a better position for imaging.

Questions to ask at the 20 week ultrasound

Your provider or the sonographer will guide you through what they’re seeing, but it’s helpful to come prepared with questions like:

• Is everything developing on track?
• Can you see the heart chambers clearly?
• How’s the placenta positioned?
• Is the umbilical cord functioning normally?
• Are there any signs of cleft palate or cleft lip?
• Are my amniotic fluid levels normal?
• What’s my baby’s estimated gestational age now?
• Is there anything that needs follow-up?

If you’re planning a gender reveal, this is often the scan that makes it possible. Be sure to tell your technician ahead of time if you want to be surprised later!

What happens after the scan?

Most people leave their anatomy scan feeling reassured – and maybe with a new favorite photo of their baby’s face or tiny feet. If everything looks good, you’ll continue with your regular prenatal visits.

If something needs more attention, your provider will explain the next steps. This could be a repeat scan in a few weeks, a consult with a specialist, or further testing.

The 20 week anatomy scan is an important checkpoint in your pregnancy, offering a close-up look at how your baby is growing. While it’s normal to feel nervous, remember: this scan is designed to give clarity not confusion. Whether you’re just hoping to see that sweet baby face or preparing to ask detailed questions about development, going into your appointment informed can help you feel empowered and calm.

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