Ascites not due to congestive heart failure in a fetus with lupus-induced heart block.

Hydrops developing in fetuses with lupus-associated heart block has usually been assumed to result from congestive heart failure. We present a case in which fetal ascites associated with complete heart block resolved promptly after administration of betamethasone and prednisone to the mother, who had anti-SSA and who developed clinical lupus erythematosus. This resolution occurred with no demonstrable change in fetal cardiac function. We conclude that an immune mechanism, rather than congestive heart failure, was responsible for the fetal ascites.