This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
Regarding IUGR 
Select and explain. 
A. Abdominal circumference (AC) is the least sensitive parameter for detection of IUGR, B. In asymmetric IUGR head circumference/abdominal circumference (HC/AC) is reduced, C. Serial biparietal diameter (BPD) is the only important measurement in IUGR, D. AC indirectly reflects fetal liver size and glycogen storage
D: AC indirectly reflects fetal liver size and glycogen storage
Answer: D: AC indirectly reflects fetal liver size and glycogen storage 
Explanation: ‘AC is the single most sensitive parameter to detect IUGR’
Dutta Obs 7/e, p 462
‘Serial measurements of AC (not BPD) and estimation of fetal weight are more diagnostic to fetal growth restriction’
Dutta Obs 7/e, p 462
Head circumference (HC) and abdominal circumference (AC) ratios: In a normally growing fetus the HC/AC ratio exceeds 1.0 before 32 weeks. It is approximately 1.0 at 32 to 34 weeks. After 34 weeks, it falls below 1.0. If the fetus is affected by asymmetric IUGR, the HC remains larger. The HC/AC is then elevated. In symmetric IUGR, both the HC and AC are reduced. The HC/AC ratio remains normal. Using HC/AC ratio, 85% of IUGR fetuses are detected
Pathophysiology: Basic pathology in small for gestational age is due to reduced availability of nutrients in the mother or its reduced transfer by the placenta to the fetus. It may also be due to reduced ultilization by the fetus. Brain cell size (asymmetric–SGA) as well as cell numbers (symmetric-SGA) are reduced. Liver glycogen content is reduced. AC indirectly reflects the decreased fetal liver size and glycogen content.