What is a typical frequency range for obstetric ultrasound?

• A. 1 to 2 MHz
• B. 2 to 3 MHz
• C. 3 to 5 MHz
• D. 5 to 7 MHz

Answer: (C)

In obstetric ultrasound, the typical frequency range used is indeed between 3 to 5 MHz. This frequency range strikes a balance between providing adequate resolution and maintaining sufficient penetration to visualize the structures of interest within the fetus and the surrounding anatomy. Higher frequencies, such as those exceeding 5 MHz, offer improved resolution but may have reduced penetration, making them less effective for imaging deeper structures or larger fetuses. Conversely, lower frequencies like those in the range of 1 to 2 MHz are primarily suited for deeper tissues and are not optimal for the detailed imaging required during obstetric examinations. Therefore, the choice of 3 to 5 MHz represents a standard practice for ensuring that images are both clear and detailed, while still allowing for sufficient depth of penetration necessary for effective assessment in obstetric cases.