Patients with hypoplastic left heart syndrome (HLHS) with intact atrial septum have an increased mortality rate. This presentation occurs in 6% to 10% of cases. We present a patient with fetal diagnosis of HLHS with restrictive atrial septum. We performed a cesarean section at 37 weeks of gestation, and under ex utero intrapartum treatment proceeded with a median sternotomy and transatrial stenting for left atrial decompression due to findings of intact atrial septum on the fetal echocardiogram performed during the procedure. Subsequently, the patient underwent hybrid stage I palliation followed by a comprehensive stage II procedure at five months of age, but unfortunately died from postoperative complications.