## Correct Answer: C. 1 vein and 2 arteries The umbilical cord is a vital fetal structure that connects the developing fetus to the placenta. A normal, healthy umbilical cord contains **three blood vessels**: two umbilical arteries and one umbilical vein. The umbilical arteries (paired) carry deoxygenated blood and fetal metabolic waste from the fetus to the placenta, while the single umbilical vein carries oxygenated, nutrient-rich blood from the placenta back to the fetus. This anatomical configuration is constant across all healthy pregnancies and is one of the first things assessed during antenatal ultrasound screening (typically at the 18–20 week anatomy scan as per Indian antenatal care guidelines). The presence of two arteries and one vein is so consistent that deviation from this pattern—such as a **single umbilical artery (SUA)**—is considered an anatomical anomaly and warrants further investigation for associated chromosomal abnormalities (trisomy 13, 18, 21) and intrauterine growth restriction. This is a fundamental embryological fact tested in obstetrics and is essential knowledge for any clinician involved in antenatal care, delivery, or neonatal assessment in the Indian healthcare setting. ## Why the other options are wrong **A. 2 arteries and 2 veins** — This is incorrect because the umbilical cord contains only ONE vein, not two. While the presence of two arteries is correct, the addition of a second vein is anatomically impossible in normal development. This option may trap students who confuse the umbilical circulation with systemic venous anatomy or who misremember the embryological derivation of these vessels. **B. 1 artery and 1 vein** — This is incorrect because the umbilical cord normally contains TWO arteries, not one. A single umbilical artery is a pathological finding associated with chromosomal abnormalities and IUGR, not the normal anatomy. Students may select this if they confuse the umbilical circulation with a simplified or symmetrical vascular model. **D. 1 artery and 2 veins** — This is incorrect because the umbilical cord contains TWO arteries and ONE vein—the reverse of this option. This is a classic NBE trap that reverses the correct numbers to test whether students have memorized the exact anatomy or merely guessed. The presence of two veins would be highly unusual and is not seen in normal development. ## High-Yield Facts - **Normal umbilical cord anatomy**: 2 arteries + 1 vein (never 2 veins or 1 artery in healthy pregnancies) - **Single umbilical artery (SUA)** is a marker for chromosomal abnormalities (trisomy 13, 18, 21) and intrauterine growth restriction; requires detailed fetal anatomy scan - **Umbilical arteries** carry deoxygenated blood and waste from fetus to placenta; **umbilical vein** carries oxygenated, nutrient-rich blood from placenta to fetus - **Antenatal ultrasound screening** at 18–20 weeks (per Indian ANC guidelines) includes assessment of umbilical cord vessels as part of routine fetal anatomy survey - **Wharton's jelly** (gelatinous connective tissue) surrounds the three vessels and protects them from compression during labor ## Mnemonics **UAV Rule** **U**mbilical cord has **A**rteries (2) and **V**ein (1) — remember: 2 As, 1 V. The arteries are paired (like kidneys), the vein is singular (like the heart's main return). Use this when examining any umbilical cord or reviewing antenatal ultrasound reports. **SUA = Sick Umbilical Artery** **S**ingle **U**mbilical **A**rtery is abnormal and associated with syndromes (trisomy, IUGR). If you see only 1 artery instead of 2, think chromosomal abnormality and growth restriction. Helps distinguish normal from pathological anatomy instantly. ## NBE Trap NBE reverses the numbers in option D (1 artery + 2 veins) to trap students who know the concept but haven't memorized the exact count. The trap exploits the assumption that if 2 arteries are correct, then perhaps 2 veins might also be plausible—testing precise anatomical recall rather than conceptual understanding. ## Clinical Pearl During delivery in Indian hospitals, the umbilical cord is routinely inspected for the presence of three vessels—a quick visual or palpation check can identify single umbilical artery at birth, prompting immediate neonatal screening for chromosomal abnormalities and cardiac defects. This simple bedside assessment has significant prognostic implications for the newborn's first week of life. _Reference: DC Dutta's Textbook of Obstetrics (Chapter on Placenta and Umbilical Cord); OP Ghai's Essential Pediatrics (Chapter on Fetal Circulation and Umbilical Cord)_
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