RhD Frequency and Maternal Alloimmunisation Among Pregnant Women Attending Federal Medical Centre, Asaba, Nigeria: Implications for Preventing Foetal and Newborn Haemolytic Disease

Abstract

Background: Maternal alloimmunisation against the RhD antigen remains a preventable cause of haemolytic disease of the foetus and newborn (HDFN), a condition responsible for substantial perinatal morbidity and mortality in resource-limited settings. Population-specific data on RhD phenotype frequency and alloimmunisation burden are critical to designing appropriate antenatal prophylaxis programmes in sub-Saharan Africa. Objectives: To determine the frequency of the RhD-negative phenotype and the prevalence of maternal alloimmunisation among pregnant women attending a tertiary antenatal clinic in Asaba, Delta State, south-south Nigeria, and to examine the age and parity distribution of RhD-negative women. Methods: A prospective, observational, cross-sectional study was conducted among 200 pregnant women of varying gravidity attending the antenatal clinic of Federal Medical Centre Asaba. RhD phenotyping was performed using standard tube agglutination with polyclonal anti-D antisera. Indirect antiglobulin test (IAT) was performed on the sera of all RhD-negative women using pooled group O red cells and antihuman globulin to screen for clinically significant alloantibodies. Ethical approval was obtained from the hospital's Health Research and Ethics Committee. Results: RhD-positive phenotype was identified in 192/200 (96.0%) and RhD-negative in 8/200 (4.0%) participants. The majority of participants were in the 31–35-year age group (37.0%) and were primigravid (48.0%). Among the 8 RhD-negative women, 1 (12.5%) was alloimmunised, corresponding to an overall alloimmunisation rate of 0.5% of the total cohort. No alloantibodies were detected in RhD-positive women. Conclusions: The RhD-negative frequency of 4.0% is consistent with reported values for south-south Nigeria and broader sub-Saharan African populations. An alloimmunisation rate of 12.5% among RhD-negative women signals a clinically meaningful burden that warrants universal antenatal antibody screening, structured anti-D immunoprophylaxis, and systematic screening of all RhD-negative women regardless of parity.