Intérêt de la technique de microtitrage des anticorps anti-RH1 dans le suivi immunohématologique des femmes enceintes

[Management of feto-maternal red cell allo-immunizations]

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.

Rh D foeto-maternal alloimmunization prophylaxis with anti-D immunoglobulins reviewed in the era of foetal RHD genotyping

In Belgium, prevention of anti-D immunization is currently based on systematic postnatal prophylaxis associated with targeted antenatal injection in high-risk situations of foeto-maternal haemorrhage.The failures of prevention are mainly due to the non-respect of established guidelines for RhlG prophylaxis, and to spontaneous undetected foetal-maternal haemorrhages without any obvious cause during the third trimester of pregnancy. In order to reduce the rate of residual post-pregnancy anti-D immunization, several countries decided to associate the classical prophylaxis to a routine antenatal anti-D prophylaxis (RAADP) during the 28th or 29th week of gestation. Since a few years, the foetal RHD genotyping in maternal plasma enables us to limit the antenatal prophylaxis only to those D- women carrying a D+ foetus. This paper deals with: the advantages of an antenatal prevention in the light of non-invasive foetal RHD genotyping, the rules rendering prevention protocols efficient whatever the algorithm applied, and the recommended immuno-haematology follow-up of women who received RhlG.