This study aimed to identify sonographic factors that can distinguish between late intrauterine growth restriction (IUGR) fetuses and constitutionally small for gestational age (SGA) fetuses. The researchers reviewed 548 cases of singleton pregnancies that delivered after 32 weeks with birth weights under the 10th percentile. Cases were classified as IUGR if complications occurred. The study found the cerebroplacental ratio (CPR), which measures placental and brain blood flow, was the most predictive of adverse outcomes. CPR values below the 5th percentile, using gestational age adjusted cut-offs, were more frequent in the IUGR group and best distinguished the two groups. A low CPR after 32 weeks was the