Fetal Intraperitoneal Immunoglobulin for Autoimmune Myocarditis and AV Block: First Clinical Experience in 5 Fetuses

Maternal anti-SSA/SSB antibodies may cause fetal myocarditis, endocardial fibroelastosis, hydrops, and atrioventricular block, with high mortality despite conventional therapies.

We report to our knowledge the first clinical experience with fetal intraperitoneal immunoglobulin (IPIG) in 5 fetuses with immune-mediated myocarditis and conduction abnormalities. At 21 to 27 weeks' gestation, each fetus received IPIG (1 g/kg estimated fetal weight) under ultrasound guidance, in addition to maternal dexamethasone. All fetuses demonstrated rapid resolution of hydrops, regression of endocardial fibroelastosis, improved myocardial performance index, and shorter atrioventricular intervals. Two fetuses with second-degree atrioventricular block reverted to sinus rhythm after repeat dosing. All neonates were liveborn; one infant died at 7 months from pneumonia unrelated to cardiac status.

This case series demonstrates the feasibility and potential safety of IPIG as a novel fetal immunomodulatory therapy. Although outcomes were encouraging, efficacy cannot be established without larger comparative studies.