In plain words
The anatomy scan is a detailed ultrasound usually done between about 18 and 22 weeks of pregnancy. The sonographer looks at the baby's brain, heart, spine, kidneys, stomach, limbs, and face. The scan also checks the placenta, the amount of fluid, and the baby's growth. It can find some differences, but it does not find everything. A normal scan is reassuring, though it is not a guarantee. If something is unclear, you may be asked to come back or to see a specialist. Many parents also enjoy seeing the baby on screen. You can ask in advance what the scan will and will not check.
The deeper version
The second-trimester anatomy survey, often called a level II ultrasound, is performed at 18 to 22 weeks and evaluates fetal structures and the placenta in standardized views, as described in ACOG Practice Bulletin 175 (2016, Ultrasonography in Pregnancy) and the AIUM practice guideline for the detailed fetal anatomic examination. Detection rates for major anomalies vary with operator skill, body habitus, gestational age, and anomaly type. Cardiac and some central nervous system anomalies are detected less reliably than skeletal or renal ones. Fetal growth is assessed by estimated fetal weight, and a third-trimester growth scan is common in practice but not universally recommended. Incidental findings such as choroid plexus cysts are common and carry low risk in isolation. The controversy concerns the volume of incidental findings and the anxiety they produce.
Where it comes up
- Prenatal tests and ultrasounds: what each one isPregnancy: Your Body
- Pregnancy at 35 and olderPregnancy: Your Body
What mothers here say about anatomy scan
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Sources
- American College of Obstetricians and Gynecologists — Practice Bulletin 175: Ultrasonography in Pregnancy (2016)
- American Institute of Ultrasound in Medicine — Practice guideline for the performance of the detailed fetal anatomic ultrasound examination