Examination of amniotic fluid in diagnosing congenital syphilis with fetal death.

The diagnosis of congenital syphilis is difficult, particularly in stillborn fetuses, who are often macerated and have undergone autolysis. These changes can obscure both syphilitic histologic findings and special stains for spirochetes in tissue specimens used to confirm the diagnosis of congenital syphilis. Five gravidas with untreated syphilis and fetal deaths underwent sonographic examination and amniocentesis. In all five cases, dark-field microscopic examination of the amniotic fluid showed spirochetes with morphology and motility characteristic of Treponema pallidum. Organisms were infrequent, but easily identified at 400x magnification and confirmed using an oil-immersion objective yielding a 900x magnification. After delivery, fetal-placental examination and autopsy showed clinical findings typical of congenital syphilis in all five cases. Histologic changes compatible with syphilis were found in all four autopsied fetuses. Silver impregnation stains were positive in two of five tissue specimens, and anti-treponemal monoclonal antibody immunofluorescence assays were positive in one of three amniotic fluid specimens examined retrospectively, further strengthening the specificity of the dark-field microscopic identification of spirochetes. This technique, which can make the diagnosis of congenital syphilis, is recommended for women with syphilis and a fetal death, especially if sonographic hydrops and/or edema is present or if an autopsy will not be performed.