Premature foramen ovale restriction/closure in pregnancy: echocardiographic features and overlap with aortic...

Evaluation of the foramen ovale (FO) is essential for understanding right heart predominance in the fetal circulation during the third trimester. Rather than considering the FO as a simple orifice, it should be assessed as a complex anatomical and functional system. Premature FO restriction or closure represents a clinically relevant but diagnostically challenging condition in fetal echocardiography.

We conducted a monocentric retrospective study including 600 uncomplicated pregnancies between 22 and 38 weeks of gestation that underwent fetal echocardiography at the Cardiology Service of ASP Reggio Calabria between January and December 2023. The FO was assessed by evaluating septum primum morphology and mobility, ostium secundum configuration, and interatrial shunt direction and magnitude on color Doppler, together with indirect hemodynamic markers. All examinations were conducted by a single operator. All pregnancies resulted in term deliveries with normal neonatal outcomes, and postnatal follow-up lasted 6-9 months.

Restrictive or premature closure of the FO was identified in 9 fetuses (incidence 1:66 pregnancies), with FO restrictiveness observed in seven cases and premature closure in two cases. Reduced interatrial shunting was defined as a limited or absent right-to-left flow across the FO on color Doppler, associated with impaired septum primum mobility and/or altered FO geometry. The most consistent indirect echocardiographic sign was right atrial dilation (100% of cases), followed by right ventricular and pulmonary artery predominance with a widely patent ductus arteriosus. In some fetuses, the FO appeared morphologically wide but functionally restrictive. All cases showed favorable early postnatal outcomes.

This study evaluates the incidence of FO restriction or premature closure in physiologically normal pregnancies during the third trimester and reviews echocardiographic features useful for its identification.