How can incomplete closure of the ductus arteriosus or foramen ovale affect my blood oxygen levels?

Variable: This depends largely on the size of the ductus arteriosus (pda) and the chronicity of the condition. At birth, if there is delayed closure of the pda, there should be no affect on oxygen levels. If the PDA is large, and long-standing, pulmonary vascular disease can develop (eisenmenger syndrome) resulting in decreased pulmonary blood flow and lower blood oxygen levels. This rarely occurs.