Correct Answer: D. Anatomical closure of foramen ovale is by 3 to 5 days
The foramen ovale does NOT undergo anatomical closure within 3 to 5 days postnatally. This is the false statement. The foramen ovale is a valve-like opening between the right and left atria that permits right-to-left shunting in fetal life when pulmonary vascular resistance is high. After birth, when the lungs expand and pulmonary vascular resistance drops, left atrial pressure exceeds right atrial pressure, pushing the septum primum against the septum secundum and functionally closing the foramen ovale within hours to days. However, anatomical fusion of the septum primum to the septum secundum occurs much later—typically by 3 months to several years of age, and in approximately 25–30% of the population it remains probe-patent throughout life without clinical consequence. The question tests knowledge of the timeline of closure of fetal shunts: ductus venosus closes functionally within 3–7 days (correct per option A), ductus arteriosus closes functionally within 2–3 weeks (correct per option B), and the right umbilical vein is indeed absent in normal fetal anatomy (correct per option C). Therefore, option D is the false statement because it confuses the functional closure (which is rapid) with anatomical closure (which is delayed), and the timeframe given (3–5 days) is far too short for true anatomical fusion.
Why the other options are wrong
A. Anatomical closure of ductus venosus is by 3 to 7 days — This statement is TRUE. The ductus venosus, which shunts umbilical venous blood directly to the inferior vena cava bypassing the liver, closes functionally when umbilical blood flow ceases at birth. Anatomical obliteration occurs within 3–7 days postnatally, forming the ligamentum venosus. This is a well-established fact in fetal circulation physiology and is NOT the false statement. B. Anatomical closure of ductus arteriosus is by 2 to 3 weeks — This statement is TRUE. The ductus arteriosus, which shunts blood from the pulmonary artery to the aorta during fetal life, closes functionally within 24–48 hours after birth due to increased oxygen tension and decreased prostaglandins. Anatomical closure (fibrosis and obliteration to form the ligamentum arteriosum) occurs within 2–3 weeks. This timeline is accurate and is NOT the false statement. C. Right umbilical vein is absent — This statement is TRUE. In normal fetal anatomy, only the LEFT umbilical vein persists and carries oxygenated blood from the placenta to the fetus. The right umbilical vein regresses during early fetal development and is absent at birth. This is a standard anatomical fact taught in embryology and is NOT the false statement.
High-Yield Facts
- Foramen ovale anatomical closure occurs by 3 months to years of age (NOT 3–5 days); functional closure is rapid but anatomical fusion is delayed.
- Ductus venosus closes anatomically within 3–7 days, forming the ligamentum venosus.
- Ductus arteriosus closes anatomically within 2–3 weeks, forming the ligamentum arteriosum.
- Probe-patent foramen ovale persists in ~25–30% of the population without clinical significance.
- Right umbilical vein regresses during fetal development; only the left umbilical vein is present at birth.
Mnemonics
Fetal Shunt Closure Timeline (DVA rule) Ductus venosus: 3–7 Days | Arteriosus: 2–3 weeks | Atrial (foramen ovale): months to years. Use this to distinguish rapid functional closure from delayed anatomical closure of the foramen ovale. Umbilical Vessels: 2 Arteries, 1 Vein (AAV) Two umbilical Arteries (deoxygenated blood to placenta) + one umbilical Vein (oxygenated blood from placenta). The RIGHT vein regresses; only LEFT vein persists. Helps rule out option C as false.
NBE Trap
NBE pairs the rapid functional closure of the foramen ovale (hours to days) with anatomical closure to trap students who conflate the two processes. The 3–5 day timeframe is plausible for functional closure but is a classic distractor for anatomical fusion, which takes months to years.
Clinical Pearl
In Indian neonatal practice, a patent foramen ovale detected on echocardiography in the first week of life is physiological and requires no intervention—functional closure occurs spontaneously. However, persistent probe-patent foramen ovale in older children or adults is clinically silent in most cases and is an incidental finding, not a disease requiring closure unless associated with paradoxical embolism or other complications.
_Reference: Robbins & Cotran Pathologic Basis of Disease, Ch. 12 (Congenital Heart Disease); Harrison's Principles of Internal Medicine, Ch. 235 (Congenital Heart Disease)_