Correct Answer: A. It has one artery and two veins
The umbilical cord normally contains two arteries and one vein, not one artery and two veins. This is the critical anatomical fact that makes option A false. The two umbilical arteries (derived from the internal iliac arteries) carry deoxygenated fetal blood from the fetus to the placenta, while the single umbilical vein carries oxygenated blood from the placenta back to the fetus. This 2:1 arterial-to-venous ratio is constant across all normal pregnancies and is a fundamental embryological principle. The presence of a single umbilical artery (SUA) is a significant finding—occurring in 0.5–1% of singleton pregnancies in Indian populations—and is strongly associated with chromosomal abnormalities (trisomy 13, 18, 21) and structural anomalies (cardiac, renal, limb defects). During routine obstetric ultrasound screening in India, identification of SUA mandates detailed fetal anatomy assessment and consideration of karyotyping. The other statements are all true: normal cord length is 50–60 cm (short cords <30 cm increase risk of intrauterine growth restriction; long cords >80 cm increase nuchal cord and entanglement risk), and Wharton's jelly is the protective gelatinous mucoid connective tissue surrounding the vessels.
Why the other options are wrong
B. Normal average umbilical cord length is 50-60 cms — This is TRUE. The normal umbilical cord length ranges from 50–60 cm, with an average of 55 cm. This is a well-established obstetric measurement. Short cords (<30 cm) are associated with intrauterine growth restriction and placental insufficiency, while excessively long cords (>80 cm) increase the risk of nuchal cord, true knots, and cord entanglement—all recognized complications in Indian obstetric practice. C. Presence of a single umbilical artery is associated with congenital anomalies — This is TRUE. Single umbilical artery (SUA) is a significant marker for fetal anomalies. It is associated with trisomy 13, 18, and 21 in 15–30% of cases, and with structural defects (cardiac, renal, gastrointestinal, limb anomalies) in 20–40% of cases. Indian obstetric guidelines recommend detailed ultrasound evaluation and genetic counseling when SUA is detected prenatally. D. It contains a gelatinous substance called Wharton's jelly — This is TRUE. Wharton's jelly is the protective mucoid connective tissue (rich in hyaluronic acid and proteoglycans) that surrounds the umbilical vessels. It provides mechanical protection, prevents vessel compression, and maintains cord integrity. Its presence is essential for normal fetal circulation and is routinely assessed during obstetric ultrasound.
High-Yield Facts
- Normal umbilical cord anatomy: two arteries (deoxygenated blood to placenta) and one vein (oxygenated blood from placenta)—NOT one artery and two veins.
- Single umbilical artery (SUA) occurs in 0.5–1% of singleton pregnancies and is associated with chromosomal abnormalities (trisomy 13, 18, 21) and structural anomalies in 20–40% of cases.
- Normal cord length is 50–60 cm; short cords (<30 cm) increase IUGR risk, long cords (>80 cm) increase nuchal cord and true knot risk.
- Wharton's jelly is the protective gelatinous mucoid tissue surrounding umbilical vessels; rich in hyaluronic acid and proteoglycans.
- Umbilical artery Doppler abnormalities (elevated PI/RI) in third trimester indicate placental insufficiency and warrant closer fetal monitoring in Indian obstetric practice.
Mnemonics
Umbilical Cord Vessels: AVV Rule Arteries (2) carry deoxygenated blood Away from fetus; Vein (1) carries oxygenated blood back. Remember: 2 arteries, 1 vein = 2:1 ratio. Use this when you see 'umbilical cord anatomy' in any question. SUA Anomaly Association: CRASH Cardiac defects, Renal anomalies, Anomalies (chromosomal—trisomy 13, 18, 21), Strucural defects, Hydrocephalus. When you see 'single umbilical artery,' think CRASH to recall associated anomalies.
NBE Trap
NBE exploits the common confusion between normal umbilical cord anatomy (2 arteries, 1 vein) and the false statement (1 artery, 2 veins). Students who memorize the wrong ratio or confuse arterial/venous flow direction will select the false statement as true, falling into the trap of reversing the 2:1 ratio.
Clinical Pearl
During routine second-trimester ultrasound screening in Indian antenatal clinics, identification of a single umbilical artery on axial cord imaging should trigger detailed fetal anatomy assessment and discussion of karyotyping options, as SUA carries significant risk for chromosomal and structural anomalies—a critical counseling point for Indian obstetric practice.
_Reference: DC Dutta's Textbook of Obstetrics (7th ed.), Ch. 6 (Placenta and Umbilical Cord); OP Ghai Essentials of Pediatrics (9th ed.), Ch. 1 (Fetal Development)_