A fetus with signs of hydrops is at high risk of intrauterine death. The pa
thophysiology of hydrops fetalis is still unclear. We found decreased conce
ntrations of cyclic guanosine monophosphate in fetal plasma of alloimmunize
d pregnancies complicated by hydrops fetalis, which might suggest reduced n
itric oxide production due to injury of fetal vascular endothelial cells. (
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