Prevalence of Rhesus D-negative blood type and the challenges of Rhesus D immunoprophylaxis among obstetric population in Ogbomoso, Southwestern Nigeria

Background: Rhesus incompatibility could pose a major problem in pregnancy, and it could be the cause of obstetric failure in a handful of women. Implementation of programs for antenatal and postnatal (Rhesus D) RhD immune globulin prophylaxis has led to a significant reduction in the frequency of maternal RhD alloimmunization and associated fetal and neonatal complications. Aims: To determine the prevalence of RhD negative among the pregnant population attending the antenatal clinic of a young tertiary health institution in Ogbomoso, a semi-urban town in southwestern Nigeria, and also the challenges faced by this sub-population of pregnant women. Materials and Methods: A retrospective review of the antenatal and labour records of obstetric patient attending Ladoke Akintola University of Technology Teaching Hospital (LTH), Ogbomoso, Nigeria. Variables were expressed as percentages. Result: Of the 596 booked patient who had their blood group systems determined, 563 women (94.5%) were RhD-positive, and 33(5.5%) women were RhD-negative. Almost 50% of the Rh-negative pregnant women were primipara. Twenty-three (69.7%) of the study population had a previous delivery or abortion, but only 9 (39.1%) of these had the Rhesus anti-D immunoglobulin following the delivery or the abortion. One of the RhD-negative women had been sensitized to the RhD positive antigen from the previous delivery at the time of booking the index pregnancy. Of the study population that delivered in our facility, only 11 (33.3%) received the anti-D immunoglobulin after the delivery, and financial inability to purchase the anti-D immunoglobulin was a major reason for refusing the immunoprophylaxis. Conclusion: Although the prevalence of RhD negative still remains low, and the rate of Rh-immunoprophylaxis remains quite low in our obstetric population, the risk of haemolytic disease of the newborn with its attendant perinatal morbidity and mortality is real in our community. The anti-D immunoglobulin should be made available and affordable.

Keywords: Ogbomoso, pregnant women, Rhesus negative

The ABO and the Rhesus blood group systems are the most important clinically. The Rh system was described by Landsteiner and Weiner in 1940. ^[1] Individuals with the Rh antigen on their red blood cells are referred to as Rh positive, whereas those without the antigen are Rh-negative. Unlike the ABO blood group system there is no preformed Rh antibody; only Rh-negative individuals are sensitized to produce the Rh antibody when they are transfused with Rh-positive blood. Rh incompatibility can pose a major problem in pregnancy when the mother is Rh-negative and fetus is Rh-positive. ^[2] In the event of feto-maternal transfusion, the mother become sensitized to the Rh antigen, and produces Rh antibodies that cross the placenta and cause agglutination and hemolysis of the fetal red blood cells. This disorder is referred to as hemolytic disease of the newborn (HDFN) or erythroblastosis. ^[3],[4] The index pregnancy in which the feto-maternal hemorrhage occurred is usually spared from HDFN; however, there can be serious HDFN in subsequent Rh positive pregnancies.

Implementation of programs for antenatal and postnatal RhD immune globulin prophylaxis has led to a significant reduction in the frequency of maternal RhD alloimmunization and associated fetal and neonatal complications. ^[5],[6] However, in low-and middle-income countries, like Nigeria, where prophylaxis and appropriate monitoring and intervention are not widely available, maternal RhD alloimmunization still occurs with significant perinatal morbidity and mortality and compromise of the women’s reproductive career. ^[7]

The distribution of RhD-negative varies widely; while a prevalence of greater than 14% is recorded among the Caucasians, ^[8] the prevalence among the different ethnic groups of the sub-Saharan Africa ranges between 2.4-4.5%. ^{[9],[10],[11],[12]} The distribution also varies in the different region of the same country; for instance, a prevalence of 0.7% is being reported among the pregnant population from the north central region of Nigeria, ^[13] whereas, a prevalence of 5% is being reported among the pregnant women from southwestern region of the same country. ^[14]

The aim of the present study therefore is to determine the prevalence of RhD negative among the pregnant population attending the antenatal clinic of Ladoke Akintola University of Technology Teaching Hospital (LTH), Ogbomoso, a young teaching hospital in the southwestern Nigeria. The study is also to determine the challenges faced by this sub-population of pregnant women.

The study is a retrospective review of pregnant women booked for antenatal care at LTH, Ogbomoso, from November 2011 to December 2012. Information was retrieved from the patients’ antenatal record notes, corroborated with the blood bank antenatal register and the labour ward birth register. The ABO and the RhD factor are part of the routine antenatal investigations for all booked pregnant women, and RhD-negative women are routinely screened for the presence of Rhesus D antibody. Variables were expressed as percentages.

There were 890 pregnant women booked for antenatal care at the institution during the study period; however, only 596 (67.0%) had their blood group systems determined. RhD-positive women were 563 (94.5%), and RhD-negative women constituted 33 (5.5%). Fifteen (45.5%) of the RhD negative woman were of blood group O, while 9 (27.3%), 6 (18.2%), 3 (9.1%) were of blood group A, B, and AB, respectively. Many of the RhD-negative women in this study were primipara (16, 48.5%), and 18 (51.5%) were multipara. Twenty-three (69.7%) of the study population had a previous delivery or abortion; 9 (39.1%) of these had the Rhesus anti-D immunoglobulin following the delivery or the abortion, while 10 (43.5%) did not receive the anti-D immunoglobulin, and it was not documented if the remaining 4 (17.4%) had it or not.

Eleven (33.3%) of the RhD-negative women had their initial RhD antibody checked, and one (9.1%) of these had positive antibody in serum; the initial antibody determination was not done by the remaining RhD negative women (22, 66.67%) due to financial inability to do so. Two (6.1%) women of the study group did not deliver in the facility. Of the 31 (93.9%) women of the study group that delivered in our facility, there was one (3.0%) stillbirth, and 3 (9.1%) asphyxiated babies who were admitted into special care baby unit (SCBU) of the hospital; one of these severely asphyxiated babies died after 14 hours of life, while the other two had blood transfusions for neonatal jaundice, and were discharged from the hospital in good condition. Eleven (33.3%) of the women who delivered in the facility received the Rh antibody immunoglobulin, and 20 (60.6%) did not receive the immunoprophylaxis; of the women that did not receive the immunoglobulin, 4 (20.0%) had RhD-negative babies, 7 (35.0%) had babies whose ABO blood group were incompatible with that of the mothers, 2 (10.0%) refused because that was their last pregnancy, another two also refused because there was no untoward effect for not receiving the immunoglobulin after their previous deliveries, and the remaining 5 (25.00%) because of financial inability to purchase the immunoglobulin.

The prevalence of RhD negative in the obstetric population of this study was 5.4%. This is still within the prevalence range of 4.6% and 5.7% found in the general women population at the Baptist Medical Centre (now Bowen University Teaching Hospital) and the state general hospital, respectively, both in Ogbomoso, by Bakare et al. in the year 2000. ^[15] Although a prevalence of 3.3% was found by Bakare et al. in the general population in Ogbomoso, 60% of the RhD-negative population were females. The 5.4% RhD negative prevalence in the present study is comparable to the 5% from Ibadan, ^[14] also located in the southwestern Nigeria as is Ogbomoso, but a higher figure than the 4.5% from Enugu, southeastern Nigeria. ^[16] However, this prevalence is even a far higher figure compared to the 0.7% from the north central region of the country; even in this north central region, the Yoruba ethnic group from the southwestern part of the country contributed the greatest proportion to the RhD negative obstetric population. ^[13] Therefore, it is not surprising that a prevalence of 5.4% was got in this study whose population is predominantly of Yoruba ethnic group.

Primipara constituted 48.5% of this study population. Since primipara constituted the greatest proportion of the RhD-negative obstetric population there is need for defined protocol which will make for proper and adequate management of this population so as not to compromise the reproductive career of these women. Furthermore, the fact that almost 50% of the RhD negative women in this study were primipara may be the reason why complications were few in the study population. This is further corroborated by the fact that the only intrauterine fatal demise (IUFD) and the three cases of severe neonatal jaundice occurred among the multipara. However, it was not established if the IUFD was due to HDFN, since the stillborn baby did not have the typical hydropic feature; neither was it established if the three cases of severe neonatal jaundice was due to HDFN.

Paradoxically, none of the women that did not receive the immunoprophylaxis following the previous delivery or the abortion had detectable RhD antibody. The only women with detectable alloanti-D antibody had the immunoprophylaxis after her previous delivery, and this might be a case of prophylaxis failure which had been documented in the literature. ^[17] This case of prophylactic failure may call for a change from the targeted administration of anti-D immunoglobulin which aims to prevent sensitization after the birth of RhD-positive baby and other potentially sensitizing events such as threatened abortion, miscarriage, and amniocentesis that is being practiced in our institution, and other institutions in Nigeria, ^[18],[19] to routine anti-D antenatal prophylaxis in which anti-D immunoglobulin is given to non-sensitized pregnant women during the antenatal period as being practiced in some developed countries, and has been shown to prevent prophylaxis failure, and also cost effective. ^{[20],[21],[22]}

The immunoprophylaxis rate in this study was very low as only 33.3% of the women had anti-D immunoglobulin after delivery, unlike in Enugu, southeastern Nigeria, and Abeokuta, southwestern Nigeria, where 99.3% and 44.8%, respectively, had the immunoprophylaxis. ^[16],[19] Apart from the women whose ABO blood group were incompatible with that of their babies, and those who had RhD-negative babies, the reasons given for not receiving the anti-D immunoglobulin were: Financial constraints (25%), no untoward effects in women who did not have immunoprophylaxis after their delivery (10%), the index pregnancy will be the last pregnancy (10%), financial inability to purchase the anti-D immunoglobulin had been identified to be a major reason why women don’t receive immunoprophylaxis. ^{[16],[17],[19]} A vial of anti-D immunoglobulin of 1,500 IU or 250μg costs between 12,000-15,000 naira (75-94 USD). Therefore, cost of procuring the anti-D immunoglobulin may be a stumbling block to routine anti-D antenatal prophylaxis.

The reasons given by the women for not receiving immunoprophylaxis, apart from financial inability, showed the poor knowledge of the women about Rhesus isoimmunization, and there is need to improve their knowledge via the antenatal health talk.

Although the prevalence of RhD-negative still remains low, and the rate of Rh-immunoprophylaxis remains quite low in our obstetric population, the risk of haemolytic disease of the newborn with its attendant perinatal morbidity and mortality is real in our community. The policy makers should ensure free antenatal care services that will make the management of the RhD-negative pregnant women accessible and affordable. There is also need for a management protocol for this condition, which will include both the clinicians and the laboratory physicians.

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1755-6783.168722