[Non-invasive fetal RHD genotyping: Validation of the method with 200 patients]. / RHD fœtal sur plasma maternel : validation de méthode sur 200 patientes.

BACKGROUND: Non-invasive fetal RHD genotyping is an important tool to assess the risk of fetuse's hemolytic disease of anti-D allo-immunized pregnant woman by non-invasive method. A method of genotyping has been developed in the laboratory of Lyon-GHE according to Minon's team (J Gynecol Obstet Biol Reprod 2005): exon 4, 5, and 10 are amplified by real time PCR. At first, genotyping results of 200 pregnant women have been compared with RH1 phenotype at birth. The most important parameters of validation have been tested: the sensibility and the specificity; the negative predictive value; the correlation study permitted to define criteria of biological interpretation. The validation of this method permitted to determine critical points and the limits of the method due to the minor amount of fetal DNA in the maternal plasma and existence of many variant forms of the RHD gene. CONCLUSION: We worked too in the perspective to the accreditation for our genetic laboratory.

[Management of feto-maternal red cell allo-immunizations]. / Prise en charge des allo-immunisations fœto-maternelles antiérythrocytaires.

Feto-maternal red cell alloimmunization is defined by the presence in a pregnant woman of alloantibodies directed against blood group antigens present on the red blood cells of the fetus and inherited from the father. It arises from the immune response to a first contact to these same antigens during a prior transfusion, transplant or pregnancy. The placental transfer and the fixation of the antibodies on the fetal red cells antigenic targets lead to a haemolysis in the fetus and the newborn. The resulting haemolytic disease can show different clinical forms, from a mild anaemia with neonatal hyperbilirubinemia to a major fetal damage with stillbirth caused by hydrops fetalis. The objective of management strategies of feto-maternal alloimmunization is to detect and monitor maternal alloimmunization and to appreciate the effects on the fetus or the newborn. Since a few years, some new non-invasive techniques of surveillance are used, for instance fetal RHD genotyping on maternal plasma and evaluation of fetal anaemia through velocimetry measurement of the blood flow in the middle cerebral artery. The need for a careful postnatal surveillance has to be emphasized due to the neonatal anaemia, which can be prolonged, and to the resurgence of cases of severe neonatal icteruses recently reported by the Académie de Médecine. The policy of prevention of anti-RH1 alloimmunization should also benefit from the evolution of biological techniques by allowing an improved targeting of concerned women.