A protocol-driven survey where completeness is the product — the views are prescribed, and what you did not see must be reported.
Orient first
- This is a SURVEY, not a targeted study. Its value comes from doing the same prescribed views every time, so that an abnormality is found by protocol rather than by suspicion.
- The highest-yield sections are the ones most often abbreviated: the four-chamber view AND the outflow tracts, the posterior fossa, the upper lip, and the spine in three planes.
- DETECTION RATES ARE NOT 100% for any structure, and vary with gestation, habitus, position and liquor. That is a property of the test, and the report should not imply otherwise.
- Many anomalies EVOLVE. A normal scan at 20 weeks does not exclude a lesion that will declare itself at 28 — coarctation, some cerebral and renal anomalies, and bowel pathology in particular.
- A SOFT MARKER is not an anomaly. Its significance depends entirely on prior risk and on whether it is isolated, and reporting one without that framing causes avoidable alarm.
Acquire the study
- Curvilinear abdominal probe; transvaginal for a low-lying fetal head or a difficult cervix.
- Confirm gestational age from the earliest available measurement — biometry interpretation depends on correct dating, not on today's measurements.
- Work through the prescribed view list in a fixed order, and document each view.
- If a view cannot be obtained, reposition the mother, walk her, and rescan before concluding — and if it still cannot be obtained, record it as not seen.
The manoeuvre
- Confirm number, viability, presentation and placental site, and describe the cord insertion.
- HEAD: measure BPD, HC; assess the ventricular atrium, cavum septi pellucidi, midline falx, and the posterior fossa including the cerebellum and cisterna magna.
- FACE: profile, orbits, and a clear view of the UPPER LIP.
- SPINE: longitudinal, transverse and coronal, with the overlying skin intact.
- HEART: situs and axis, four-chamber view, LEFT and RIGHT outflow tracts, the three-vessel and three-vessel-trachea views.
- ABDOMEN: measure AC; stomach on the left, kidneys, bladder, cord insertion, and the diaphragm as an intact line.
- LIMBS: measure femur length; confirm all long bones and both hands and feet with their orientation.
- Measure liquor volume and, where indicated, the cervix.
- Record explicitly which prescribed views were NOT obtained.
What confirms it
- A complete study is one in which every prescribed view was obtained and documented — completeness IS the finding.
What licenses you to exclude it
- ⚠️ A NORMAL ANOMALY SCAN DOES NOT EXCLUDE AN ANOMALY. State the detection limitation plainly rather than issuing a report that reads as an all-clear.
- Views not obtained must be listed, with a plan to repeat — an incomplete study reported without that list is the most common failure here.
- Reduced liquor, maternal habitus and fetal position each degrade sensitivity; say which applied.
The classic misread
- Reporting a study as complete when views were missed.
- Assessing the heart on the four-chamber view alone, which misses outflow tract anomalies.
- Reporting an isolated soft marker without the prior-risk framing.