**4.2 Absence of facility for foetal genotype testing for D, K and other clinically relevant red cell antigens**

Rhesus D grouping is relevant for blood donors, transfusion recipients and for women of child bearing age including pregnant women. This is because the Rh blood group antigens particularly D is significantly immunogenic. Rh D negative individuals often lack the D antigens on their red cells and can potentially be sensitised when exposed to D antigen positive red cells during pregnancy and blood transfusion. Such antibodies are often capable of causing a haemolytic transfusion reaction (HTR) and haemolytic disease of the foetus and newborn (HDFN). Since the introduction of prophylactic anti-D and implementation of evidence based best practice of careful management and monitoring of D negative pregnant women for all the potentially sensitising events that occur during pregnancy, the prevalence of HDFN because of Rh D incompatibility between the mother and baby has declined significantly [90]. In order to prevent Rhesus D negative women who are not previously sensitised from developing alloantibody D, these women are offered prophylactic anti-D during pregnancy under the Routine Antenatal Anti-D Prophylaxis program between 28 and 34 weeks' gestation. The half-life of the administered anti-D is 12 weeks. The anti-D prevents the mother from being sensitised by micro foetal maternal haemorrhage that can occur as a result of potentially sensitising events that occur during pregnancy. These women should have a fetomaternal haemorrhage testing following any potentially sensitising events that occur after from 20 weeks' gestation. This test quantifies the amount of foetal red cells that entered the maternal circulation to allow for the administration of adequate dose of anti-D to clear the fotal cells and prevent them from

sensitising the mother. Anti-D (125 IU) is required to remove 1 ml of foetal red cells from maternal circulation. RhD alloimmunisation is still a significant cause of foetal and neonatal morbidity and mortality particularly in Nigeria and other developing countries [93–95] because of absence of evidence-based best practices and non-implementation of Rh D prophylaxis during pregnancy. This often result in a significant number of unfortunate women developing alloantibody D through no fault of theirs but rather as a result of failure in stewardship by the Nigerian government. Also, non-invasive foetal blood group genotyping (DNA) testing of maternal plasma to determine the antigen status of the developing foetus carried by an alloimmunised pregnant women is vital as it provides useful information as to whether a foetus is carrying the group specific antigen and in fact at risk of HDFN. This will help prevent the need for extensive laboratory testing (titration and quantification of antibody every 4 weeks from booking till 28 weeks' gestation and every 2 weeks from 28 weeks to delivery) and clinical monitoring in antigen negative cases. Molecular testing of maternal plasma for foetal DNA can be performed during the second trimester. DNA probes for the most common antigens associated with HDFN are now available [96]. Knowledge of the molecular basis of the blood group systems has facilitated the development of assays for blood group genotyping. Foetal Rhesus D genotyping can potentially tell at 16 weeks' gestation through the analysis of amniotic fluid or through maternal plasma the foetal D genotype of the developing foetus. In previously sensitised alloimmunised pregnant women, knowledge of the foetal D antigen status is beneficial to enable obstetricians optimally manage these women [95]. In non-sensitised Rhesus negative pregnant women, the knowledge of the foetal D antigen status is quite important for several reasons; prevent us from exposing the mother to a prophylactic anti-D (a human blood product that even though significantly virally tested for TTIs) she does not need, allow for the optimal utilisation of the product in patients in whom it is indicated and spare the woman the pain of the product being administered intramuscularly. *RHD* genotyping of foetuses carried by Rh D-negative women using foetal DNA obtained invasively through amniocentesis or chorionic villus sampling used to be critical to the clinical management of these women. Technological advances now allows for accurate determination of foetal *Rh D* genotype using cell-free foetal DNA from maternal blood, thus overcoming the invasive procedures [97]. *Rh D* genotyping are based on polymerase chain reaction using non-invasive blood sample from the mum are quite sensitive with low incidence of false positive result [98, 99]. Although there are cases of D-negative genomes possessing fragments of mutated Rh D genes, the most notable of which is the Rh D pseudogene found in Africans. Rh D genotyping tests have been developed to differentiate these alleles and thus enhance the diagnosis in a multi-ethnic population [100].

Foetal blood group genotype of a developing foetus can also be determined for Rh C, c, E and Kell (K) using cffDNA from maternal plasma [101]. Many European Union countries have suggested the mass application of foetal genotyping for all foetuses carried by D-negative women. This advocacy is based on clear benefit of conserving anti-D stocks and prevention of unnecessary administration of this human-derived blood product that has associated risk [102, 103]. In Denmark and the Netherlands this evidenced-based best practice of foetal *Rh D* testing for all non-sensitised D negative pregnant women have been introduced [104]. Also, non-invasive foetal blood group genotyping (DNA) testing of maternal plasma to determine the antigen status of the developing foetus carried by an already alloimmunised pregnant women is vital as it provides useful information as to whether a foetus is carrying the group specific antigen and in fact at risk of haemolytic disease. This will help prevent the need of extensive laboratory (titration and

**123**

ate transfusion in these patients.

*Distribution of Clinically Relevant Blood Group Antigens among Nigerians…*

must be C-, D-, E- and K-, leucocyte depleted to less than 1 × 106

unit, less than 5 days old, free from clinically significant irregular blood group antibodies and negative for high-titre anti-A and anti-B haemolysin. If the mother has other alloantibodies apart from D, it is vital that suitable unit negative for the specific antigens to which those maternal alloantibodies are specific are selected. Once the baby is delivered, intensive phototherapy and IV immunoglobulin along with antiglobulin (DAT) test should be carried out. There should also be continuous monitoring of the haemoglobin, haematocrit and bilirubin level. A positive DAT is diagnostic of HDFN and the baby sample should be sent for elution to identify if the antibody coating the foetal red cell is maternal alloantibody. If the bilirubin is not responsive to intensive phototherapy and continues to rise, the associated neonatal anaemia and hyperbilirubinemia can be managed by carrying our exchange blood transfusion (EBT) to prevent bilirubin encephalopathy by removing a significant number of maternal antibodies-coated foetal red cells and excess bilirubin and replacing it with donor red cells. The red cell product used for EBT must meet certain requirements; group O or ABO compatibility (mum and baby), compatible with any maternal antibody, gamma irradiated, collected in saline, adenine, glucose and mannitol (SAGM), fresh less than 5 days old, have high haematocrit (0.5–0.55) to prevent of post-exchange anaemia and polycythaemia and negative for high titre haemolysins. A number of these evidenced-based best practices; facility for intrauterine blood transfusion, facilities for diagnosis of foetal anaemia in utero, maternal alloantibody testing, elution testing, facility for gamma irradiation of blood, CMV testing of donors units, testing of donor units for other clinical significant red cell antigens apart from ABO and Rhesus D, SAGM units and leucodepletion of donor units are often not available in Nigeria and most developing countries. This failure in stewardship by government in these countries limits the delivery of best possible care in the management of HDFN and appropri-

leucocytes per

quantification of antibody every 4 weeks till 28 weeks' gestation and every 2 weeks from 28 weeks to delivery) and clinical monitoring in antigen-negative cases.

**4.3 Absence of facility for intrauterine transfusion for children with HDFN that** 

The maternal alloantibody D produced as a result of sensitization of the Rh D negative mother to the Rhesus D positive foetal red cells are low molecular weight IgG antibody. This antibody can potentially cross the placenta barrier into the foetal circulation and can destroy the foetal red cells resulting in anaemia, heart failure, hydrops foetalis (fluid retention and swelling) and intrauterine death. In utero the diagnosis of foetal anaemia used to be made by carrying out ultrasound guided foetal blood sampling for analysis of the foetal haemoglobin and haematocrit or amniocentesis-an invasive ultrasound guided procedure with a significant 2% risk of foetal loss associated with entering the amniotic sac and obtaining amniotic fluid which is analysed for product of haemoglobin breakdown. However, non-invasive diagnosis of foetal anaemia can now be made using non-invasive Doppler ultrasound technology by measuring the middle cerebral artery peak systolic velocities (MCA PSV). The foetal anaemia can be managed with intrauterine blood transfusions. Intrauterine transfusion is associated with a number of risks; foetal bradycardia, foetal death, cord haematoma, haemorrhage from the puncture site, miscarriage, preterm labour and vessel spasm. The blood used for such transfusions must meet certain requirements; gamma irradiated red cells to prevent transfusion-associated graft-versus-host disease, haemoglobin S negative, CMV negative and significantly high PCV (0.70–0.85) [105, 106], unit

*DOI: http://dx.doi.org/10.5772/intechopen.90372*

**are severely anaemic in utero**

quantification of antibody every 4 weeks till 28 weeks' gestation and every 2 weeks from 28 weeks to delivery) and clinical monitoring in antigen-negative cases.
