Complete Heart Block in the Fetus: An Antenatal Complication of Sjögren's Syndrome

Background: Complete fetal atrioventricular block (CAVB) is a rare but life-threatening condition, occurring in approximately 1-2% of pregnancies associated with maternal anti-Ro/SSA antibodies. The transplacental migration of anti-Ro/SSA and anti-La/SSB antibodies damages the fetal cardiac system, leading to sustained bradycardia, cardiomyopathy, fetal hydrops, and intrauterine fetal demise. Despite the use of fluorinated corticosteroids or β-agonists, therapeutic efficacy remains limited once a complete block is established. Case Presentation: We present the case of a 35-year-old primigravida with a pregnancy achieved through in vitro fertilization (IVF). At 20 weeks of gestation, she was referred to our emergency unit due to persistent fetal bradycardia. Fetal echocardiography confirmed CAVB with a ventricular rate of 64 bpm. Maternal serologic testing was positive for anti-Ro/SSA and anti-La/SSB antibodies, suggesting an autoimmune etiology. Treatment with oral dexamethasone and salbutamol was initiated, but follow-up echocardiography at 24 weeks showed worsening cardiac status, including reduced ventricular rate of 59 bpm, cardiomegaly, and pericardial effusion. Intrauterine fetal death occurred at 25 weeks of gestation. Management and Outcome: Four months postpartum, the patient underwent a minor salivary gland biopsy. Histopathological evaluation confirmed the diagnosis of primary Sjögren's syndrome. Conclusions: This case illustrates the severe consequences of autoimmune-mediated CAVB and the limited effectiveness of available treatments once a complete block has developed. It underscores the importance of early fetal rhythm surveillance and targeted maternal autoimmune screening-particularly before assisted reproduction, where structured preconception evaluation offers an opportunity for earlier recognition and risk stratification. Earlier detection may improve counseling and management strategies in future pregnancies.