The Anatomy Scan at 20 Weeks: What Your Provider Is Looking For

The Most Detailed Scan of Your Pregnancy

The anatomy scan, also called the mid-pregnancy ultrasound or anomaly scan, is typically performed between 18 and 22 weeks. It is the most thorough imaging your baby will receive before birth, and its purpose is both reassuring and practical: to confirm that your baby's organs and structures are developing as expected, and to give your provider a detailed look at the placenta, amniotic fluid, and uterine environment.

For most families, this scan is a milestone. It is often the first time you see recognizable features on screen, like a profile, hands, or feet. It may also be the appointment where you learn the sex of your baby, if you choose to find out.

What Your Provider Is Evaluating

The sonographer will work through a systematic checklist, measuring and documenting each major system. Here is what they are looking at:

Brain and Head

The scan evaluates the shape and structure of the skull, the brain's ventricles (fluid-filled spaces), the cerebellum, and the overall symmetry of brain development. Measurements of the head circumference (HC) and biparietal diameter (BPD, the distance across the skull) are recorded.

Face

The sonographer will look for the presence of both lips and check the palate for clefting. You may get a clear view of your baby's profile, though facial images depend on the baby's position and cooperation.

Heart

The fetal heart receives particular attention. Your provider will examine the four chambers, the outflow tracts (the vessels carrying blood away from the heart), and the heart's rhythm. The heart is one of the most complex structures to evaluate, and certain views require the baby to be in specific positions. If a complete cardiac assessment is not possible during the scan, you may be asked to return for a follow-up.

Spine

The entire length of the spine is examined for alignment and closure. The sonographer checks that each vertebra is properly formed and that the skin covering the spine is intact.

Kidneys and Bladder

Both kidneys should be visible, and the bladder is checked for the presence of fluid, which confirms that the baby is swallowing amniotic fluid and producing urine.

Stomach

The stomach should appear as a small dark bubble, indicating that the baby is swallowing normally. An absent or unusually large stomach may prompt additional evaluation.

Limbs

All four limbs are assessed for length and symmetry. The sonographer measures the femur length (FL) as one of the standard growth parameters.

Placenta

The placenta's position is documented. If the placenta is lying low or covering the cervix (called placenta previa), your provider will plan a follow-up scan later in pregnancy. In many cases, as the uterus grows, the placenta moves away from the cervix on its own.

Amniotic Fluid

The amount of amniotic fluid surrounding the baby is assessed. Both too much (polyhydramnios) and too little (oligohydramnios) can warrant further monitoring.

Umbilical Cord

The sonographer confirms that the cord has three vessels: two arteries and one vein. A two-vessel cord (single umbilical artery) occurs in a small percentage of pregnancies and may lead to additional monitoring, though most babies with a two-vessel cord develop normally.

Understanding Soft Markers

During the anatomy scan, your sonographer may note what are called "soft markers." These are minor ultrasound findings, such as an echogenic intracardiac focus (a bright spot on the heart), a choroid plexus cyst (a small cyst in the brain), or a slightly dilated kidney, that are common in healthy pregnancies but can, in some studies, be associated with a mildly increased chance of chromosomal differences.

Here is the key point: soft markers are not diagnoses. Many of them resolve on their own as pregnancy progresses, and the vast majority of babies with one or even two soft markers are perfectly healthy. If a soft marker is identified, your provider will consider it alongside your other screening results, your age, and the overall picture rather than treating it as an isolated finding.

If the presence of a soft marker causes you concern, ask your provider to explain the actual statistical significance in the context of your pregnancy. Informed conversations are more useful than isolated data points.

Finding Out the Sex

The anatomy scan is the most common time to learn the baby's sex through ultrasound. If you want to know, let your sonographer know at the start of the appointment. If you prefer to wait, say that clearly as well, so they can avoid revealing it accidentally.

Keep in mind that visibility depends on the baby's position. Sometimes the angle does not allow a clear view, and certainty is not always possible. Ultrasound-based sex determination is highly accurate at 20 weeks, but no imaging method is 100 percent definitive.

When Findings Need Follow-Up

In most cases, the anatomy scan confirms that everything looks as expected, and no further imaging is needed. When findings do require follow-up, the most common next steps include:

• A repeat anatomy scan if the baby's position prevented complete visualization of a structure (the heart is the most common reason for a callback).
• A fetal echocardiogram, a specialized ultrasound of the baby's heart performed by a pediatric cardiologist or maternal-fetal medicine specialist.
• Growth scans later in pregnancy if the baby is measuring notably smaller or larger than expected.
• A consultation with a maternal-fetal medicine (MFM) specialist if a structural concern is identified.

A callback does not necessarily mean something is wrong. Many callbacks are simply about getting a better look.

What to Bring and How Long It Takes

The anatomy scan typically runs 30 to 60 minutes, longer if the baby is not in an ideal position or if the sonographer needs additional views. Bring a support person if you would like. Some offices allow older children, but check ahead.

You generally do not need a full bladder at 20 weeks, though your provider's office may have specific instructions. Wear comfortable, two-piece clothing so your abdomen is easy to access.

Bring a list of any questions you have been saving. This is a natural checkpoint to discuss upcoming prenatal visits, any screening results, and your evolving birth preferences.

Every Family's Scan Is Different

Some families eagerly anticipate the anatomy scan for months. Others feel anxious about what it might reveal. Both responses are completely normal. If you find yourself worried, it may help to know that the vast majority of anatomy scans confirm healthy development. And if a finding does arise, it is the beginning of a conversation and a plan, not a final answer.

Searching for Providers on BAABY

Whether you are looking for an OB-GYN, a midwife, or a maternal-fetal medicine specialist to help interpret results and guide next steps, BAABY's provider directory lets you search by specialty and location. Finding a provider who communicates clearly and respects your questions makes every scan feel more grounded.