Premature closure of foramen ovale results is :

B i.e., Right ventricular hyperophyBefore bih, foramen ovale allows most of the oxygenated blood entering the right atrium from inferior vena cava to pass into left atrium & prevents the opposite direction flow because the septum primum closes against relatively rigid septum secundum. After bih foramen ovale closes functionally and approximately at 3 months of age valve fuses with the septum secundum forming oval fassa. Premature closure leads to right ventricular hyperophyQ