What are the primary causes of asymmetric IUGR?

Asymmetric intrauterine growth restriction (IUGR) is primarily characterized by a discrepancy in fetal growth, where the head may be maintained at a normal size while the abdomen is smaller, indicating that there has been a restriction of fetal growth typically occurring later in pregnancy. This type of IUGR commonly results from placental insufficiency and associated vascular factors.

When placental blood flow is compromised, the fetus may not receive adequate nutrients and oxygen, leading to a preferential growth of the brain (head) over the abdominal organs, which rely more on these resources. This scenario often occurs in cases of maternal hypertension, preeclampsia, or other conditions that affect placental function or vascular health.

In contrast, causes such as maternal infections, genetic abnormalities, and multiple gestations may play a role in fetal growth restrictions, but they do not specifically lead to the asymmetric pattern seen in more significant placental and vascular issues. Maternal infections can lead to symmetric IUGR, where the entire body size is reduced evenly, and genetic abnormalities often present with various syndromic features rather than specifically causing asymmetric growth. Multiple gestations can complicate growth but often leads to symmetric IUGR as well.

Therefore, the preference for vascular