Dizygotic twin pregnancy after transfer of one embryo Marie-Louise van der Hoorn, M.D., M.Sc., Frans Helmerhorst, M.D., Ph.D., Frans Claas, Ph.D., Sicco Scherjon, M.D., Ph.D.  Fertility and Sterility  Volume 95, Issue 2, Pages 805.e1-805.e3 (February 2011) DOI: 10.1016/j.fertnstert.2010.08.026 Copyright © 2011 American Society for Reproductive Medicine Terms and Conditions

Figure 1 Four pieces of evidence strongly suggesting that the twin in this case report was dizygotic: [1] HLA typing of the mother, both children, and father; [2] macroscopic examination of the placenta; [3] histology of the dividing fetal membrane; and [4] fluorescence in situ hybridization staining of the X and Y chromosome. (A) HLA typing of five HLA antigens shows that both children inherited one set of antigens from the mother. The other set of HLA antigens is inherited from the father. By coincidence, the father and mother share five HLA antigens (blue). (B) Pictures of the placenta from the fetal side (upper picture) and from the maternal side (lower picture). These pictures show that two separate placentas were present, without vascular anastomoses. (C) May-Grünwald-Giemsa staining of the dividing fetal membrane showing that the twin was dichorionic and diamniotic. (D) Fluorescence in situ hybridization staining of two adjacent amniotic membranes. Blue stains the cell nucleus, red stains the X chromosome, and green stains the Y chromosome. The enlargement clearly shows that one amniotic membrane originates from the girl and the other from the boy. Fertility and Sterility 2011 95, 805.e1-805.e3DOI: (10.1016/j.fertnstert.2010.08.026) Copyright © 2011 American Society for Reproductive Medicine Terms and Conditions