ABSTRACT
Abstract Tetralogy of Fallot (TOF) consists of four cardiac changes: interventricular communication, pulmonary stenosis, aortic dextroposition and right ventricular hypertrophy. The prevalence is 0.1 per 1,000 live births. A primiparous mother with gestational age of 38 weeks came to the emergency. At the time, it was verified in her twin pregnancy that one fetus had TOF, thus a pregnancy interruption was scheduled for the following day. In the neonatal physical examination of both, localized acrocyanosis, regular heart rhythm with the presence of a heart murmur, and good peripheral perfusion were found. The echocardiogram of twin 1 revealed: patent foramen ovale; a wide perimembranous interventricular communication of misalignment, with the aorta riding the septum by 50%; hypertrophied and long infundibulum with pulmonary infundibulo-valvular stenosis, with a maximum systolic gradient of 66 mm Hg; both pulmonary arteries presented dimensions of 0.35 mm; pulmonary valve annulus: 0.56 mm; and patent ductus arteriosus measuring 0.19 mm. The echocardiogram of twin 2 showed: patent foramen ovale; a wide perimembranous interventricular communication of misalignment, with the aorta riding the septum by 50%; hypertrophied infundibulum with stenosis pulmonary infundibulo-valve, with a maximum systolic gradient of 33 mm Hg; reduced confluent pulmonary arteries; right pulmonary artery measuring 0.40 mm and left pulmonary artery measuring 0.55 mm; pulmonary valve annulus measuring 0.72 mm; a closed arterial canal, and mild aortic regurgitation. Tetralogy of Fallot is a multifaceted syndrome with a high prevalence in pediatrics. This case is the first case of congenital heart defect concordance for TOF in monozygotic twins in Brazil.