**Core Concept**
Cocaine use during pregnancy is associated with various congenital anomalies due to its vasoconstrictive and stimulant effects on the fetal cardiovascular system. The primary concern is the potential for cocaine to cause fetal growth restriction (FGR) and increase the risk of preterm birth.

**Why the Correct Answer is Right**
Cocaine crosses the placental barrier and can lead to vasoconstriction, reducing blood flow to the fetus. This can result in FGR, characterized by low birth weight and decreased fetal growth. Additionally, cocaine exposure can increase the risk of preterm labor and birth. The exact mechanisms involve the inhibition of catecholamine reuptake, leading to an increase in circulating catecholamines, which can stimulate uterine contractions and reduce placental blood flow.

**Why Each Wrong Option is Incorrect**
* **Option A:** While maternal use of cocaine is associated with several congenital anomalies, it is not primarily linked to neural tube defects. Neural tube defects are more commonly associated with folic acid deficiency.
* **Option B:** Maternal use of cocaine is not primarily associated with cardiac anomalies such as tetralogy of Fallot. While cocaine use can increase the risk of congenital heart defects, the primary association is with cardiac arrhythmias and ischemia.
* **Option C:** Maternal use of cocaine is not primarily associated with omphalocele. While maternal use of cocaine can increase the risk of preterm birth and FGR, it is not specifically linked to omphalocele.

**Clinical Pearl / High-Yield Fact**
Cocaine use during pregnancy is a significant risk factor for FGR and preterm birth. Healthcare providers should screen for cocaine use in pregnant women and provide appropriate counseling and support to reduce the risks associated with maternal cocaine use.

**Correct Answer:** C