Anatomy Scan (20-Week Ultrasound)
The anatomy scan is one of the most anticipated appointments of pregnancy. This detailed ultrasound — usually done between 18–22 weeks — examines every major organ and structure of your baby's body.
Typically performed: Weeks 18–22
What's Examined
The sonographer systematically checks:
- Brain structure (ventricles, cerebellum, corpus callosum)
- Face (lip and palate for cleft, eye spacing)
- Heart (four chambers, major vessels, rhythm)
- Spine (for neural tube defects)
- Kidneys and bladder
- Stomach (should be visible as it fills with swallowed amniotic fluid)
- Abdominal wall
- Limbs (length of bones, hands and feet)
- Placenta location, umbilical cord, amniotic fluid levels
- Cervical length (may be checked)
- Fetal sex (if you want to know)
How Long It Takes
Typically 30–60 minutes, sometimes longer if baby is in a challenging position. You may be asked to walk around or have a snack if the baby isn't cooperating for certain views. A full bladder often helps early in the window; practices vary in their instructions.
If Something Is Found
The vast majority of anatomy scans are completely normal. If a soft marker or concern is identified, your provider will discuss what it means, whether follow-up ultrasounds or specialist consultations are needed, and what the range of outcomes looks like. Many "soft markers" resolve or have no clinical significance.
Frequently Asked Questions
The anatomy scan can identify soft markers associated with Down syndrome (such as shortened femur length or absent nasal bone), but it is not a chromosomal test. NIPT or amniocentesis provide more definitive chromosomal information.
Fetal sex can typically be determined at 18–20 weeks by ultrasound. Accuracy is very high (98%+) at this stage, though it depends on baby's position.
You may be asked to walk, eat, or return for a second scan if the baby won't move into the right position for all required views. This is common and not cause for concern.