1. Obstetric ultrasound dating measurements
Obstetric ultrasound dating measurements. A: Transverse axial sonogram of the fetal head. This is a typical plane of section used to measure the biparietal diameter (BPD) across the head (from one electronic caliper to the other). The head circumference (HC) can also be measured. This is a perimeter measurement around the fetal calvarium. B: Transverse axial sonogram of the fetal abdomen. This is the plane of section frequently used to measure the abdominal circumference (AC). This is also a perimeter measurement. C: Sonogram demonstrating the measurement of the fetal femur length (FL). The femur is measured from its calcified proximal to distal aspect. D: This chart demonstrates the four typical fetal measurements utilized in trying to define gestational age. The ultrasound age is usually an average of the four measurements–BPD, HC, AC, and FL–and is reported in menstrual weeks (MA). The result is always related to the patient's recollection of the first day of her last normal menstrual period (LMP); EDD, estimated date of delivery; EFW, estimated fetal weight (grams); CI, cephalic index (relationship of the measurement of the fetal head from front to back and side to side). (Used, with permission, from Peter W. Callen, MD.)
Source: Obstetrics & Obstetric Disorders, Current Medical Diagnosis & Treatment 2017
Citation: Papadakis MA, McPhee SJ, Rabow MW. Current Medical Diagnosis & Treatment 2017; 2016 Available at: Accessed: December 25, 2017
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