The Anatomy Scan: What the 20-Week Ultrasound Reveals

The 20-week anatomy scan is one of the most significant milestones in your pregnancy. This guide explains what the ultrasound measures, how to prepare, and what to expect during this detailed look at your baby's development.

second-trimester 8 min read
The Anatomy Scan: What the 20-Week Ultrasound Reveals

TL;DR

The anatomy scan (level II ultrasound) is a detailed prenatal screening typically performed between 18 and 22 weeks of pregnancy. It systematically evaluates your baby's organs, limbs, and overall growth, as well as the placenta and amniotic fluid, to ensure healthy development and identify any potential structural concerns.

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Important

Contact your doctor immediately if you experience sharp abdominal pain, heavy vaginal bleeding, or a sudden gush of fluid before your scheduled ultrasound appointment.

In This Article

What Exactly is the 20-Week Anatomy Scan?

The anatomy scan, also called a level II ultrasound or fetal anomaly scan, is a comprehensive medical examination that uses high-frequency sound waves to create detailed images of your baby's developing body.

While earlier ultrasounds are often focused on confirming the pregnancy and checking the heartbeat, the 20-week scan is a systematic, 'head-to-toe' evaluation. At Viva Eve, we perform this screening between 18 and 22 weeks of pregnancy, a window when the baby's organs are large enough and developed enough to be seen clearly on the screen. This appointment is usually longer than your standard prenatal checkup, often lasting 45 to 60 minutes. It is a medical screening first and foremost, though for many families, it's also a deeply emotional moment where the baby feels more 'real' than ever before. Our sonographers work carefully to capture specific measurements required by clinical guidelines while ensuring you feel comfortable and informed throughout the process.

What Does the Sonographer Measure During the Scan?

During the scan, the sonographer evaluates the baby's brain, heart, spine, kidneys, and limbs, while also checking the position of the placenta and the volume of amniotic fluid.

The sonographer follows a detailed checklist to ensure every major system is functioning as expected. They will look at the structures of the brain (the ventricles and cerebellum), the four chambers of the heart, the alignment of the spine, and the presence of both kidneys and the bladder. They will also count the fingers and toes and measure the length of the long bones in the arms and legs. Beyond the baby's body, we look at the 'support system.' This includes checking the location of the placenta to ensure it isn't covering the cervix (a condition called placenta previa) and measuring the amniotic fluid levels. We also examine the umbilical cord to confirm it has three vessels, which is the standard for optimal nutrient delivery.
If you want to know the sex of your baby, the 20-week scan is usually the time it can be determined with high accuracy. However, this depends on the baby's position. If the legs are crossed or the cord is in the way, the sonographer might not be able to get a clear view. If you prefer it to be a surprise, just let us know at the start of the appointment!

How Should I Prepare for My Appointment?

Preparing for your anatomy scan involves wearing comfortable clothing and, in some cases, having a partially full bladder to help lift the uterus for a clearer view.

Unlike early first-trimester ultrasounds, you usually don't need a completely full bladder for the 20-week scan, but having some fluid can help. We recommend drinking a glass of water about 30 minutes before you arrive. Wear a two-piece outfit (like pants and a loose shirt) so we can easily access your abdomen without you needing to undress completely. You might find that having a light snack or a bit of fruit juice before the appointment makes the baby more active, which can help the sonographer get the angles they need. Most importantly, bring your partner or a support person. This is a lot of information to take in, and having a second set of ears—and someone to share the excitement with—makes the experience much better.

What Happens if the Sonographer Finds Something Unusual?

If an abnormality or 'soft marker' is identified, it does not always mean there is a problem. It usually indicates that more detailed testing or a follow-up ultrasound is needed to gather more information.

It is completely normal to feel a surge of anxiety if the sonographer gets quiet or asks for a second opinion. In many cases, they just need a better angle or the baby needs to move. If we do see something that requires a closer look, we distinguish between 'soft markers' and 'hard findings.' A soft marker (like an echogenic intracardiac focus or a choroid plexus cyst) is often a variation of normal development that disappears on its own. A hard finding is a clear structural issue that may require a referral to a Maternal-Fetal Medicine (MFM) specialist. At Viva Eve, we guide you through every step of this process, explaining what we see in plain language and arranging any necessary follow-up care immediately.

Common Questions About the 20-Week Ultrasound

Most patients have questions about the safety of ultrasound, the accuracy of the results, and whether they will receive photos of their baby during the appointment.

Ultrasound technology has been used for decades and is considered safe for both you and your baby when performed by trained medical professionals. It does not use radiation (like X-rays). While the scan is very accurate at detecting major structural issues, it is important to remember that it is a screening tool, not a guarantee. Some conditions may not be visible on ultrasound. Yes, you will get to see your baby! We usually provide printed or digital images for you to take home. However, remember that the sonographer's priority is the medical checklist. They may spend a long time looking at one organ in silence to ensure they get the right measurement, but they will always make time to show you the 'fun' parts, like the profile or a waving hand.

Navigating the Emotions of the Mid-Pregnancy Milestone

The anatomy scan is often a mix of intense joy and nervous anticipation. Acknowledging these feelings as a normal part of the parenting journey can help you feel more grounded.

We often see couples walk into our Forest Hills or Manhattan suites with a mix of 'Christmas morning' excitement and 'final exam' jitures. Both are valid. You are at the halfway point of your pregnancy, and the stakes feel higher now that you can feel the baby moving and see their growing personality on the screen. If the scan reveals everything is on track, the relief is immense. If it brings up new questions, it can feel like a sudden detour in your plans. No matter the outcome, our team is here to support the person behind the patient. We don't just treat conditions; we care for families. If you're feeling overwhelmed, don't hesitate to talk to us—we're here to walk this path with you.
Common Questions

Frequently Asked Questions

The scan can look for 'soft markers' associated with Down syndrome, such as a thickened nuchal fold or certain heart variations. However, it is not a diagnostic test. For a definitive answer, you would need a blood test (NIPT) or a diagnostic procedure like an amniocentesis.

Most anatomy scans take between 45 and 60 minutes. If the baby is in a difficult position or if you are carrying multiples, it may take longer. We recommend blocking out at least 90 minutes for your total visit to allow for check-in and discussion with your doctor.

No. A medical anatomy scan is performed using 2D ultrasound, which provides the clearest 'cross-section' images for medical diagnosis. 3D and 4D scans are often used for 'keepsake' images to see the baby's face, but they are not a substitute for the clinical 20-week screening.

If the baby is sleeping or in a position that hides their heart or spine, the sonographer might ask you to go for a short walk, drink some cold water, or change positions. Sometimes, we may even schedule a brief follow-up visit a week later to finish the measurements.

If you have an anterior placenta (meaning it's attached to the front wall of your uterus), you don't need to do anything differently for the scan. It may slightly cushion the sound waves or make it take a bit longer to get certain angles, but it doesn't affect the accuracy of the anatomy scan.

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