OBSTETRICAL ULTRASOUND

Obstetrical ultrasound uses low-energy, high-frequency sound waves.

Figure I-3-1. First-Trimester   Obstetrical U/S Showing Crown   Rump

Length

Early   first-trimester ultrasound  utilizes    a   crown–rump  (CRL)   measurement.

Later   second- and third-trimester ultrasound  utilizes    four    measurements:

biparietal  diameter    (BPD), head circumference   (HC),   abdominal

circumference   (AC),   and femur   length  (FL).