Rapid diagnosis of trisomy 18 and dizygosity in twins using fluorescence in situ hybridization on uncultured amniocytes

Background: The diagnosis of a chromosomally abnormal third trimester fetus prior to birth permits optimal obstetrical management and psychological support for the parents when the child is born. Although ultrasound findings may lead to suspicion of Edward syndrome, confirmation of the diagnosis depends on the cytogenetic detection of trisomy 18. Certain obstetrical situations may limit the choice of diagnostic procedures to amniocentesis when a rapid cytogenetic result in required. Case: Fluorescence in situ hybridization in uncultured amniocytes permitted rapid detection of trisomy 18 in one twin following preterm labor, allowing a definitive diagnosis before birth. Conclusion: The technique described enables a rapid, targeted cytogenetic result using uncultured amniocytes. This is a valuable new tool when a specific fetal aneuploidy is strongly suggested by sonography and obstetrical factors preclude the use of procedures other than amniocentesis.