Equal distribution of congenital blood cell chimerism in dizygotic triplets after in-vitro fertilization

The special situation of multiple pregnancies following IVF has led to a gr owing interest in the assessment of embryonal development by means of molec ular genetics. We report a case of congenital blood chimerism in dizygotic triplets (two boys, one girl) present in erythrocytes and leukocytes in bot h sexes. Routine pre-operative blood serology of the 6 year old female trip let revealed chimerism of the red cells. Flow cytometry of the erythrocytes and DNA analysis of the leukocytes demonstrated that all three children ha d the same proportions of male and female cells. Fluorescent in-situ hybrid ization (FISH) analyses revealed Y chromosomes in 84% of the girl's leukocy tes and in 89/92% of the two boys' leukocytes. The true genetic lines were determined by analysing polymorphism of serum groups (glycoprotein, transfe rrin, protease inhibitor and plasminogen) secreted by non-haematopoetic tis sue, by blood group typing of hair roots and by DNA analysis of endothelial cells. Evidently placental anastomoses allowed a reciprocal intra-uterine transfusion of blood stem cells in the triplets.