**Core Concept**
A single umbilical artery in newborns is a congenital anomaly associated with various fetal and maternal complications. The normal umbilical cord contains two arteries and one vein, which are formed by the fusion of the vitelline arteries, umbilical arteries, and vitelline veins during embryonic development.

**Why the Correct Answer is Right**
A single umbilical artery is often an indicator of underlying fetal anomalies, such as renal agenesis, omphalocele, or cardiac defects. The presence of a single umbilical artery is thought to result from the failure of one of the vitelline arteries to regress during embryonic development. This anomaly can lead to increased blood pressure and flow through the remaining artery, potentially causing vasoconstriction and reduced placental perfusion. Furthermore, the risk of intrauterine growth restriction (IUGR) and stillbirth is higher in pregnancies with a single umbilical artery.

**Why Each Wrong Option is Incorrect**
**Option A:** While maternal hypertension can have adverse effects on fetal development, it is not directly related to the presence of a single umbilical artery.
**Option B:** Fetal distress can be a consequence of various factors, including placental insufficiency, but it is not the most direct association with a single umbilical artery.
**Option C:** Congenital heart defects are a possible association with a single umbilical artery, but they are not the most common or direct consequence.

**Clinical Pearl / High-Yield Fact**
A single umbilical artery is a significant finding that warrants further investigation, including a detailed ultrasound examination and possibly a fetal echocardiogram, to rule out underlying fetal anomalies.

**Correct Answer:** D.