Pendahuluan: Transposisi arteri besar (TGA) adalah kelainan jantung bawaan pada anak yang terjadi akibat ketidaksesuaian pertukaran sistem arterioventrikular, yang menyebabkan sianosis pada bayi baru lahir. Tulisan ini melaporkan kasus TGA yang didiagnosis melalui ultrasonografi prenatal dan kemudian menjalani prosedur balloon atrial septastomy (BAS) setelah lahir.Kasus: Seorang ibu berusia 33 tahun hamil dengan janin yang dicurigai TGA berdasarkan hasil ekokardiografi janin melalui visualisasi outflow tract paralel dan transposisi arteri pulmonalis di tengah antara aorta dan vena cava superior pada potongan RVOT, yang awalnya didiagnosis pada usia kehamilan 34 minggu. Perencanaan persalinan dan perawatan pascakelahiran dipersiapkan melalui kolaborasi multidisiplin antara divisi fetomaternal, perinatologi, kardiologi anak, dan ahli bedah kardiotoraks. Setelah bayi lahir, segera dilakukan ekokardiografi yang menunjukkan TGA dan defek septum atrium (ASD) kecil, selanjutnya bayi baru lahir segera menjalani prosedur BAS oleh kardiologi pediatrik. Kesimpulan: Diagnosis prenatal ultrasonografi TGA memungkinkan perencanaan persalinan, perawatan perinatologi dan prosedur BSA sebelum tindakan bedah.A case report of Transposition of Great Arteries (TGA): Prenatal DiagnosisAbstract Introduction: Transposition of the Great Arteries (TGA) is a pediatric congenital heart defect that occurs in incompatibility of the arterioventricular exchange system, which results in cyanosis in a newborn baby. We reported a case of TGA that was diagnosed by prenatal ultrasonography and then underwent a balloon atrial septostomy (BAS) procedure after birth.Case Report: A 33-year-old mother pregnant with a fetus suspected of TGA based on the results of prenatal fetal echocardiography through visualization of a parallel outflow tract and transposition of the pulmonary artery in the middle between the aorta and superior vena cava at RVOT level, which initially diagnosed at 34 weeks of gestational age. Birth planning and perinatal care were prepared through multidisciplinary collaboration between the fetomaternal division, perinatology, pediatric cardiology, and cardiothoracic surgeon. After the baby was born, an echocardiography was immediately performed, showing TGA and small ASD, and then the newborn had BAS procedure by pediatric cardiology.Conclusion: A prenatal diagnosis of TGA through ultrasonography provides a better outcome that allows for labor planning, perinatology care, and BAS procedures before surgery.Key word : TGA, ccTGA, ASD, Transposition of Great Arteries.