What type of IUGR is characterized by head sparing?

The type of intrauterine growth restriction (IUGR) characterized by head sparing is known as asymmetrical IUGR. In this condition, the fetal head remains relatively proportional or preserved in size while the body shows evidence of underdevelopment or growth restriction.

This preservation of head size typically occurs because the brain is one of the last organs to be affected by the restrictions in blood flow and nutrient supply. In cases of asymmetrical IUGR, the fetus has undergone some form of stress or inadequate supply of nutrients, which leads to a more significant reduction in the body's growth compared to the growth of the brain.

Symmetrical IUGR, on the other hand, is characterized by a proportional decrease in both head and body size, which occurs early in the pregnancy, often due to genetic factors or maternal conditions affecting fetal growth. Severe and moderate IUGR classifications primarily concern the extent of restriction but are not as indicative of the head-sparing phenomenon seen in asymmetrical IUGR.