A headache in prenatal diagnosis: A case of vanished twin or hermaphroditism?

Introduction: The finding of a mixture of both 46,XX and 46,XY cells in amniotic fluid culture has been frequently described. In the great majority of cases, the finding is followed by the birth of a normal male infant, leading to a consensus that the finding is the result of contamination with maternal cells in a normal male fetus. There are, however, several other possible explanations including the presence of cells from an undiagnosed twin pregnancy, cross contamination in the laboratory, the presence of cells from a "vanished" male twin, and true fetal chimerism. An accurate obstetric history and thorough sonography can be of great value in correct assessment of such situations. Materials and Methods: A 29 Years-old woman was referred for genetic counseling. Her gestational age was 16 weeks and maternal biochemical serum screening test indicated high risk for Down Syndrome. She underwent amniocentesis for chromosome study using standard high resolution GTG banding technique. Results: Karyotype result was 46,XY and sonography revealed a female fetus with normal internal genital organs. A normal baby girl was borned with 46,XX karyotype. Upon reviewing of amnio GTG slides both 46,XY and 46,XX cell lines were detected. The patient admitted that she had experienced a miscarriage and heavy bleeding early in pregnancy. The sonography at the time of amniocentesis had shown a shrinking cyst next to the fetus. These findings strengthened the vanished or resorbed twin as the reason for such a finding. Conclusion: The fetus was most likely a non-identical twin. Most of grown cells were from the vanished male fetus which led to misdiagnosis. Thorough genetic counseling with the view of obstetric history is of great value in such situations. [ABSTRACT FROM AUTHOR]