title: Interphase FISH--assisted second-trimester termination of a trisomy 21 fetus in an IVF-ET twin pregnancy. A case report.
abstract: BACKGROUND
  When confronting a dizygotic pregnancy with one fetus affected with chromosomal aberrations, most couples would opt for selective termination of the affected twin.
  
  
  METHODS
  Routine genetic amniocentesis was performed for an in vitro fertilization-embryo transfer twin pregnancy at 18 weeks' gestation due to advanced maternal age. After two weeks, cytogenetic analysis revealed that both twins were male and one was affected with trisomy 21. At that time, ultrasound examination could not tell them apart with certainty. With the aid of interphase fluorescence in situ hybridization (FISH), we had no trouble locating the affected twin and performed feticide successfully with an intracardiac potassium chloride injection. At 37 weeks of gestation, a normal male was delivered along with a macerated trisomy 21 fetus.
  
  
  CONCLUSIONS
  In a dizygotic twin pregnancy discordant for chromosome aberrations, when ultrasound cannot distinguish the affected twin, performing interphase FISH with an appropriate chromosome probe proves very useful in quickly and accurately locating the chromosomally abnormal twin for selective termination.
authors.affiliation: Department of Obstetrics and Gynecology, Chang Gung Memorial Hospital, Lin-Kou Medical Center, Tao-Yuan, Taiwan.
authors.forename: S D
authors.initials: SD
authors.lastname: Chang
authors.forename: A S
authors.initials: AS
authors.lastname: Chao
authors.forename: Y M
authors.initials: YM
authors.lastname: Lai
authors.forename: H Y
authors.initials: HY
authors.lastname: Liu
authors.forename: Y K
authors.initials: YK
authors.lastname: Soong
mesh_terms: D000328:Adult; D003937:Diagnosis, Differential; D004314:Down Syndrome / Q000235:genetics*; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007231:Infant, Newborn; D007399:Interphase; D008297:Male; D011247:Pregnancy; D011256:Pregnancy Outcome; D018607:Pregnancy Reduction, Multifetal; D011262:Pregnancy Trimester, Second; D014429:Twins, Dizygotic / Q000235:genetics*