fetal pole
Early embryonic structure visible on ultrasound, representing the developing fetus before distinct anatomical features are apparent.
Full Definition
The earliest ultrasound-visible structure representing the developing embryo, typically observed between 6-7 weeks of gestational age within the gestational sac. The fetal pole appears as a linear echogenic structure adjacent to the yolk sac and is the first sign of embryonic development. Crown-rump length measurements begin once the fetal pole is clearly visualized, and cardiac activity should be detectable when the fetal pole reaches 5-7mm in length. Absence of a visible fetal pole when expected may indicate embryonic demise or miscalculated gestational age.
Usage
Usage note: Always correlate fetal pole measurements with gestational age calculations.
In Context
- "A 6mm fetal pole was visualized with positive cardiac activity at 6 weeks 2 days." — Early pregnancy ultrasound report
- "No fetal pole was identified despite an appropriately sized gestational sac." — Viability assessment ultrasound