Final answer:
The difference between symmetric and asymmetric intrauterine growth restriction (IUGR) lies in the pattern of fetal growth. Symmetric IUGR results in a uniform reduction in the size of organs and body parts, often due to early pregnancy issues, while asymmetric IUGR leads to a more severe restriction in abdominal and organ size than in the head, usually due to placental issues occurring later in pregnancy.
Step-by-step explanation:
The difference between symmetric and asymmetric intrauterine growth restriction (IUGR) concerns the growth and development of the fetus during pregnancy. Symmetric IUGR is a condition where the fetus has an overall delay in growth, affecting all body systems and organs proportionately. On the other hand, asymmetric IUGR typically presents when the growth of the fetus's abdomen and organs is more severely restricted compared to the head and brain.
Asymmetric IUGR is usually caused by placental insufficiency that occurs later in pregnancy. This type of growth restriction allows for the preferential redirection of nutrients to the brain, known as 'brain-sparing.' This adaptation is an effort by the fetus to maintain growth in the most vital organs when nutrients or oxygen are limited. Conversely, symmetric IUGR tends to arise due to issues earlier in pregnancy, such as chromosomal abnormalities or infections, which affect the fetus's growth potential globally.