title: Confined blood chimerism in a monochorionic dizygotic sex discordant twin pregnancy conceived after induced ovulation.
abstract: BACKGROUND
  Monochorionic twins are generally considered as a monozygotic twin pregnancy. However, several cases of monochorial dizygotic twin pregnancies have been reported.
  
  
  METHODS
  We report on a rare case of monochorionic dizygotic twin pregnancy conceived after induced ovulation in a 32-year-old woman. The diagnosis was made on morphological ultrasound examination at 18+4 weeks of gestation, showing two fetuses with discordant sex. The amniocentesis was declined by the patient.
  
  
  RESULTS
  The monochorionic status was confirmed after a histopathalogical study of the placenta. At delivery, both a phenotypically normal boy and a phenotypically normal girl without sexual abnormality were observed. This analysis also revealed the presence of vascular anastomoses between both fetal circulations. Postnatal cytogenetic analyses indicated the presence of a chimerism in peripheral blood lymphocytes. This chimerism was not observed in cells obtained from a buccal swab. Molecular determination of zygosity confirmed the existence of the confined peripheral blood chimerism with the presence of four parental alleles.
  
  
  CONCLUSIONS
  We report on a case of monochorionic dizygotic twin pregnancy. This observation underlies the need to carefully assess twin pregnancies, especially when obtained after assisted reproductive technology.
authors.affiliation: Service d'Histologie Embryologie et Cytogénétique, Hôpitaux Universitaires Paris Sud, Site Antoine Béclère, APHP, Clamart, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Mayeur Le Bras
authors.affiliation: Laboratoire de Génétique Moléculaire, Hôpitaux Universitaires Paris Sud, Site Antoine Béclère, APHP, Clamart, France.
authors.forename: François
authors.initials: F
authors.lastname: Petit
authors.affiliation: Service de Gynécologie-Obstétrique, Hôpitaux Universitaires Paris Sud, Site Antoine Béclère, APHP, Clamart, France.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Benachi
authors.affiliation: Service de Gynécologie-Obstétrique, Hôpitaux Universitaires Paris Sud, Site Antoine Béclère, APHP, Clamart, France.
authors.forename: Bettina
authors.initials: B
authors.lastname: Bedel
authors.affiliation: Service de Néonatalogie, Hôpitaux Universitaires Paris Sud, Site Antoine Béclère, APHP, Clamart, France.
authors.forename: Salima
authors.initials: S
authors.lastname: Oucherif
authors.affiliation: Unité de Fœtopathologie, Hôpitaux Universitaires Paris Sud, Site Antoine Béclère, APHP, Clamart, France.
authors.forename: Jelena
authors.initials: J
authors.lastname: Martinovic
authors.affiliation: Service d'Histologie Embryologie et Cytogénétique, Hôpitaux Universitaires Paris Sud, Site Antoine Béclère, APHP, Clamart, France.
authors.forename: Narjes
authors.initials: N
authors.lastname: Armanet
authors.affiliation: Service d'Histologie Embryologie et Cytogénétique, Hôpitaux Universitaires Paris Sud, Site Antoine Béclère, APHP, Clamart, France.
authors.forename: Lucie
authors.initials: L
authors.lastname: Tosca
authors.affiliation: Service d'Histologie Embryologie et Cytogénétique, Hôpitaux Universitaires Paris Sud, Site Antoine Béclère, APHP, Clamart, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Gautier
authors.affiliation: Service d'Histologie Embryologie et Cytogénétique, Hôpitaux Universitaires Paris Sud, Site Antoine Béclère, APHP, Clamart, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Parisot
authors.affiliation: Service de Pédiatrie, Hôpitaux Universitaires Paris Sud, Site Antoine Béclère, APHP, Clamart, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Labrune
authors.affiliation: Service d'Histologie Embryologie et Cytogénétique, Hôpitaux Universitaires Paris Sud, Site Antoine Béclère, APHP, Clamart, France.
authors.forename: Gérard
authors.initials: G
authors.lastname: Tachdjian
authors.affiliation: Service d'Histologie Embryologie et Cytogénétique, Hôpitaux Universitaires Paris Sud, Site Antoine Béclère, APHP, Clamart, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Brisset
mesh_terms: D000328:Adult; D046528:Chimerism; D005260:Female; D006801:Humans; D008297:Male; D010062:Ovulation Induction; D011247:Pregnancy; D014429:Twins, Dizygotic
keywords: ART; assisted reproductive technology; confined peripheral blood chimerism; monochorionic dizygotic twins