Prenatal Diagnosis of Immune-Mediated Fetal Complete Heart Block Revealing Maternal Systemic Lupus Erythematosus.

Immune-mediated congenital heart block (CHB) is a rare but severe manifestation of neonatal lupus, resulting from transplacental transfer of maternal anti-SSA/Ro and anti-SSB/La antibodies. It is associated with significant fetal and neonatal morbidity and mortality and may reveal previously undiagnosed maternal autoimmune disease. We report the case of a 34-year-old multigravida woman with no known systemic disease, referred at 29 weeks of gestation for suspected fetal arrhythmia. Fetal echocardiography revealed complete atrioventricular block associated with myocardial hypertrophy and pericardial effusion. Maternal immunologic screening demonstrated high titers of anti-SSA/Ro and anti-SSB/La antibodies, leading to the diagnosis of systemic lupus erythematosus. Despite multidisciplinary management and antenatal planning, the neonate developed severe postnatal bradyarrhythmia and heart failure, resulting in death on day 4 of life. This case highlights the pathogenic mechanisms, diagnostic challenges, and therapeutic strategies of immune-mediated CHB. Early detection through serial fetal echocardiography and maternal antibody screening is essential, as established complete CHB remains largely irreversible. Preventive therapy with hydroxychloroquine has emerged as the most effective strategy to reduce recurrence risk by more than 50% in subsequent pregnancies, based on recent prospective trials. Immune-mediated CHB may be the first manifestation of maternal autoimmune disease. Systematic immunologic screening, close fetal surveillance, and preventive treatment with hydroxychloroquine are crucial to optimize maternal and neonatal outcomes.