INTRAUTERINE GROWTH

RESTRICTION

The common definition of intrauterine growth restriction (IUGR) (also known
as fetal growth restriction) is a fetus with estimated fetal weight (EFW) <5−10th
percentile for gestational age. This assumes the fetus is not growing to its genetic
potential.

Another definition is <2,500 grams (5 lb, 8 oz). Clearly, neonatal morbidity and
mortality are affected by lowering birth weight. However, 70% of these fetuses
are constitutionally small.

Dating. Accurate early pregnancy dating is essential for making the diagnosis.
An early sonogram (<20 weeks) is most accurate if conception date is unknown.
Don’t change gestational age based on a late sonogram.

Fetal Causes. Examples include aneuploidy (e.g., T21, T18, T13); infection
(e.g., TORCH), structural anomalies (e.g., congenital heart disease, neural tube
defects, ventral wall defects). These causes typically lead to symmetric IUGR.

Placental Causes. Examples include infarction, abruption, twin-twin transfusion
syndrome (TTTS), velamentous cord insertion. These causes typically lead to
asymmetric IUGR.

Maternal Causes. Examples include hypertension (e.g., chronic, preeclampsia),
small vessel disease (e.g., SLE, long-standing type 1 diabetes), malnutrition,