title: Monozygotic twins discordant for monosomy 21 detected by first-trimester nuchal translucency screening.
abstract: BACKGROUND
  Chromosomal abnormality in one fetus of a monozygotic twin pregnancy is rare, and discussion of prenatal detection of such a case offers some insight into this clinical problem.
  
  
  METHODS
  A 28-year-old gravida 1 had ultrasound screening at 11 weeks of gestation that revealed a monochorionic, diamniotic twin pregnancy with increased nuchal translucency (7.7 mm) in one fetus. Subsequent evaluation showed one 45,XY,-21 karyotype and one normal male karyotype. The pregnancy was monozygous by DNA analysis. The affected neonate died 5 minutes after delivery of both twins by cesarean.
  
  
  CONCLUSIONS
  Monochorionic twins discordant for fetal abnormalities can be evaluated with molecular analysis. Study of such cases may reveal the extent to which an early diagnosis can lead to therapeutic interventions to support survival of the viable twin.
authors.affiliation: Department of Obstetrics and Gynecology, Chang Gung Memorial Hospital, Taiwan. pjcheng@cgmh.org.tw
authors.forename: Po-Jen
authors.initials: PJ
authors.lastname: Cheng
authors.forename: Sheng-Wen
authors.initials: SW
authors.lastname: Shaw
authors.forename: Jin-Chung
authors.initials: JC
authors.lastname: Shih
authors.forename: Yung-Kuei
authors.initials: YK
authors.lastname: Soong
mesh_terms: D000328:Adult; D002891:Chromosomes, Human, Pair 21 / Q000235:genetics*; D004200:Diseases in Twins / Q000235:genetics*; D005260:Female; D005865:Gestational Age; D006801:Humans; D009006:Monosomy; D009333:Neck / Q000000981:diagnostic imaging* / Q000196:embryology*; D011247:Pregnancy; D011263:Pregnancy Trimester, Third; D016216:Ultrasonography, Prenatal