Anne Mayeur Le Bras1, François Petit2, Alexandra Benachi3, Bettina Bedel3, Salima Oucherif4, Jelena Martinovic5, Narjes Armanet1, Lucie Tosca1, Valérie Gautier1, Frédéric Parisot1, Philippe Labrune6, Gérard Tachdjian1, Sophie Brisset1. 1. Service d'Histologie Embryologie et Cytogénétique, Hôpitaux Universitaires Paris Sud, Site Antoine Béclère, APHP, Clamart, France. 2. Laboratoire de Génétique Moléculaire, Hôpitaux Universitaires Paris Sud, Site Antoine Béclère, APHP, Clamart, France. 3. Service de Gynécologie-Obstétrique, Hôpitaux Universitaires Paris Sud, Site Antoine Béclère, APHP, Clamart, France. 4. Service de Néonatalogie, Hôpitaux Universitaires Paris Sud, Site Antoine Béclère, APHP, Clamart, France. 5. Unité de Fœtopathologie, Hôpitaux Universitaires Paris Sud, Site Antoine Béclère, APHP, Clamart, France. 6. Service de Pédiatrie, Hôpitaux Universitaires Paris Sud, Site Antoine Béclère, APHP, Clamart, France.
Abstract
BACKGROUND: Monochorionic twins are generally considered as a monozygotic twin pregnancy. However, several cases of monochorial dizygotic twin pregnancies have been reported. CASE REPORT: 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. CONCLUSION: 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.
BACKGROUND: Monochorionic twins are generally considered as a monozygotic twin pregnancy. However, several cases of monochorial dizygotic twin pregnancies have been reported. CASE REPORT: 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. CONCLUSION: 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.