Red blood cell alloimmunization in pregnancy.

Division of Maternal-Fetal Medicine, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7516, USA.
Seminars in Hematology (Impact Factor: 2.46). 08/2005; 42(3):169-78. DOI: 10.1053/j.seminhematol.2005.04.007
Source: PubMed

ABSTRACT Red blood cell (RBC) alloimmunization in pregnancy continues to occur despite the widespread use of both antenatal and postpartum Rhesus immune globulin (RhIG), due mainly to inadvertent omissions in administration as well as antenatal sensitization prior to RhIG given at 28 weeks' gestation. Additional instances are attributable to the lack of immune globulins to other RBC antigens. Evaluation of the alloimmunized pregnancy begins with the maternal titer. Once a critical value [32 for anti-Rh(D) and other irregular antibodies; 8 for anti-K and -k] is reached, fetal surveillance using serial Doppler ultrasound measurements of the peak velocity in the fetal middle cerebral artery (MCA) is standard. In the case of a heterozygous paternal phenotype, amniocentesis can be performed to detect the antigen-negative fetus that requires no further evaluation. MCA velocities greater than 1.5 multiples of the median necessitate cordocentesis, and if fetal anemia is detected, intrauterine transfusion therapy is initiated. A perinatal survival of greater than 85% with normal neurologic outcome is now expected. Future therapies will target specific immune manipulations in the pregnant patient.

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    ABSTRACT: Haemolytic disease of the fetus and the newborn [HDFN] is caused by incompatibility of maternal and fetal erythrocytes. Red blood cell alloimmunization is a well-known cause of HDFN. Due to heterogeneity of populations, the spectrum of alloimmunization varies around the world. This study aimed to determine the frequency of alloimmunization in pregnant women and to determine the risk of HDFN in our population. This was a descriptive study conducted at Aga Khan University Hospital Karachi. Blood type and red cell antibody screening was determined on every pregnant woman at her first antenatal visit. Red cell antibody identification was performed on positive screening results. A total of 1000 pregnant females including 633 (63.3%) multigravida were studied. Blood type B was predominant (n = 374 or 37.4%) and D negative was observed in 136 women (13.6%). No red cell antibody was detected in 982 females (98.2%). 20 red cell antibodies were detected in 18 women (1.8%). The incidence of non-anti-D was 16/1000 [1.6%] in all pregnant females. The non-anti-D alloantibodies included anti-M (n = 3; 15%), anti-Lewis(a) (n = 3; 15%), anti C ( n = 1; 5%), anti-E (n = 1; 5%), anti-e (n = 1; 5%), anti-Lewis(b) (n = 1; 5%) and nonspecific antibodies (n = 6; 30%). The incidence of anti-D was 4/136 or 2.9% in D negative blood type. After excluding prior sensitization due to blood transfusions, risk remained was 2.2%. Antibodies of clinical significance were identified in 9 (0.9%) females. In our cohort, frequency of red cell alloimmunization during pregnancy was 1. 8% out of which 0.9% were clinically significant antibodies posing a risk for HDFN. Despite prenatal and post natal prophylaxis, risk of sensitization with D antigen in D negative women was high at 2.2%. We recommend that all pregnant women should be screened for irregular antibodies irrespective of the rhesus type. Copyright © 2014. Published by Elsevier Ltd.
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