Your Anatomy Scan
A simple guide to the ultrasound you will have in the middle of your pregnancy.
Around the middle of your pregnancy, you will be offered a special ultrasound. People call it the anatomy scan (or the 20-week scan). This guide walks you through it step by step, before your visit, so you know what to expect.
It takes about 5 minutes to read. You can use the Next and Back buttons at any time.
Most anatomy scans bring good news. This guide is here to help you feel ready and to know what questions you may want to ask.
What this guide is built on
- AIUM Practice Parameter for the Performance of Standard Diagnostic Obstetric Ultrasound. J Ultrasound Med. 2024;43(6):E20–E32. doi:10.1002/jum.16406 — the current, jointly developed standard for what the scan checks.
- AIUM–ACR–ACOG–SMFM–SRU Practice Parameter for the Performance of Standard Diagnostic Obstetric Ultrasound Examinations. J Ultrasound Med. 2018;37(11):E13–E24. doi:10.1002/jum.14831 — defines the parts of the body checked and the recommended timing of 18–22 weeks.
- American College of Obstetricians and Gynecologists. Ultrasound Exams. ACOG patient FAQ. — plain-language source on the purpose and timing of pregnancy ultrasound.
What is the anatomy scan?
The anatomy scan is a detailed ultrasound. An ultrasound uses sound waves — not X-rays — to make a picture of your baby on a screen. It is safe and it does not hurt.
This scan gives your care team a careful look at how your baby is growing and how the body is forming.
The best time for this scan is 18 to 22 weeks of pregnancy. At this point, organs like the heart and brain are large enough to see clearly.
Why this scan matters
- It checks the size and growth of your baby.
- It looks at the main organs and body parts as they form.
- It checks the placenta (the organ that feeds your baby), the fluid around your baby, and where your baby is lying.
- If you want to know, it can often show the baby's sex.
Getting ready
There is not much you need to do. A few simple things can make the visit go smoothly.
How long it takes
This is often the longest ultrasound of your pregnancy. Plan for about 30 to 60 minutes. It can take longer if your baby is in a position that makes some parts hard to see.
About a full bladder
Some clinics ask you to drink water and come with a full bladder. Others do not. Follow what your own clinic tells you, since advice can be different from place to place.
What to wear
Wear comfy clothes you can move easily. You will need to show your belly, so a top you can lift and pants you can lower work well.
- Ask your clinic if you can bring a support person, and how many guests are allowed.
- Write down any questions ahead of time. (This guide helps you build a list in a moment.)
- Ask if your clinic gives keepsake pictures, and if you can take photos.
During the scan
Here is what usually happens, step by step.
- You lie down on a table and show your belly.
- A person called a sonographer (an ultrasound expert) puts a warm gel on your skin. The gel helps the sound waves travel.
- They move a smooth handheld tool, called a transducer, across your belly. This is the part that takes the pictures.
- They take many pictures and measurements. You may see them freeze the screen or draw small lines to measure your baby.
- They may ask you to roll a little or take a sip of water to help your baby move into a better spot.
The sonographer often stays quiet while they work, because they are focusing and measuring carefully. Quiet does not mean something is wrong. They simply need to concentrate.
What the scan looks at
Tap each part below to see what the team checks, from head to toe. These are the parts of a standard scan.
The team measures the size of the head and looks at the shape of the brain and the spaces inside it.
Why: head size helps check growth, and the brain's shape helps show that it is forming well.
They look at the face, including the upper lip.
Why: this can help find things like a cleft lip (a gap in the lip).
They follow the spine from the neck down to the lower back.
Why: to check that the bones of the back are lined up and the skin over them is closed.
They look at the heart, including a view that shows its four chambers and the large blood vessels leaving it. They also look at the chest.
Why: the heart is complex, so the team checks it with extra care.
Inside the belly, they find the stomach, the two kidneys, and the bladder.
Why: to check that these organs are present and in the right place.
They check the cord where it joins your baby's belly and count the blood vessels inside it.
Why: a typical cord has three vessels, and the team confirms this.
They check that the arms and legs are present and measure the long bones, such as the thigh bone.
Why: bone lengths help check growth, and the team confirms the limbs are there.
Beyond the baby, they check the placenta and where it sits, the amount of fluid around your baby, and the way your baby is lying.
Why: these tell your team about your baby's home and support during pregnancy.
Parents often hope to see ten fingers and ten toes. The team checks that the hands and feet are there, but a perfect count of every finger and toe is not always possible, and that is normal.
Finding out the sex
If you want to know your baby's sex, the anatomy scan is often when you can find out.
By 18 to 22 weeks, the body parts that show sex are usually formed enough to see. But not always.
- If your baby is lying in a way that hides those parts, the team may not be able to tell that day.
- If you do not want to know, tell the team at the start so they can avoid sharing it.
There is no right or wrong choice here. It is fully up to you.
What the results mean
For most families, the anatomy scan brings reassuring news.
It is a screening test, not a promise
A scan is a way to look closely, but it cannot find every condition. There are honest limits to what any ultrasound can show:
- Some conditions are very small or hard to see.
- Some conditions develop later in pregnancy, after this scan.
- The picture can be harder to get depending on your baby's position, the amount of fluid, or your own body.
None of these limits mean something is wrong. They are simply the reason a scan cannot promise a perfect picture.
If the team wants a closer look
Sometimes the team will ask you to come back, or will suggest another test or a visit with a specialist. This is common, and it does not always mean there is a problem. Often it just means a part was hard to see and they want a clearer view.
It is normal to feel nervous. More information is meant to help your care team support you and your baby. If anything is unclear, your clinician or midwife will explain what it means and what happens next.
Your questions
Tap any questions you may want to ask at your visit. Then make your own list to print or keep.
Before you go — a few reminders
- The anatomy scan is safe and does not hurt.
- The best time is between 18 and 22 weeks.
- It checks your baby's growth and main body parts, plus the placenta and fluid.
- It is a careful look, but it cannot find every condition.
- Most scans bring reassuring news.
It does not replace your clinician or midwife, and it is not for emergencies. For any concern about your pregnancy, call your clinician or midwife. If you feel you may need urgent help, contact your local emergency services.