Which ultrasound biometric is the best single predictor of fetal growth abnormalities?

• A. Abdominal circumference
• B. Femur length
• C. Extraocular and transcerebellar diameters
• D. Head circumference

Answer: (A)

Abdominal circumference is the best single predictor of fetal growth abnormalities because it reflects fetal nutrition and liver size, which drive most of the fetal weight gain. When growth is restricted, liver size and subcutaneous fat decrease first, causing the abdominal circumference to fall earlier and more reliably than other measurements. Head circumference and femur length can stay relatively normal for a while due to the brain-sparing effect and later overall size reduction, so they’re less sensitive indicators of early growth problems. Measurements of extraocular and transcerebellar diameters are useful for brain development assessment and dating, but they don’t track overall fetal growth as directly as abdominal circumference. In clinical practice, serial AC measurements correlate best with estimated fetal weight and help detect fetal growth restriction more effectively than the other biometric parameters.