Burden of rhesus isoimmunization and pregnancy outcomes: a cross-sectional study conducted at Kenyatta National Hospital, Kenya

¹Department of Obstetrics and Gynaecology, School of Medicine, University of Nairobi, Nairobi, Kenya, ²Monitoring, Evaluation, Research and Learning, Amref Health Africa, Nairobi, Kenya

^&Corresponding author
John Abayo Otieno, Department of Obstetrics and Gynaecology, School of Medicine, University of Nairobi, Nairobi, Kenya

Introduction    

The ABO and rhesus (Rh) systems remain the most clinically significant blood group antigens on red blood cell membranes [1]. The Rh system consists of two related proteins, RhD and RhCE, which express the D and CE antigens, respectively. Individuals with the RhD antigen are Rhesus positive (RhD+), while those without it are rhesus negative (RhD-) [1]. Globally, the prevalence of RhD-negative blood varies by population, being highest among the Basques of Spain (35%), followed by Caucasians 14% [2], and lowest among sub-Saharan African populations between 2.4 and 4.5% [3]. In Kenya, the prevalence has been reported at approximately 3.9% [4]. The relatively low prevalence in African populations [5] does not negate its clinical importance due to the serious consequences of rhesus isoimmunization, also known as Rh incompatibility [6]. Rhesus iso immunization occurs when an RhD-negative mother is exposed to RhD-positive fetal red blood cells, leading to the production of maternal anti-D antibodies. These antibodies can cross the placenta in subsequent pregnancies and destroy fetal red blood cells, resulting in hemolytic disease of the fetus and newborn. The clinical manifestations range from mild jaundice and anemia to hydrops fetalis, stillbirth, and neonatal death [7,8].

This occurs either from feto-maternal haemorrhage through escape of the foetal cells through the placenta or from incompatible blood transfusion [9]. Predisposing factors for feto-maternal haemorrhage include delivery, spontaneous or induced abortion, ectopic pregnancy, miscarriage, intrauterine foetal death, abdominal trauma, antepartum haemorrhage, amniocentesis, chorionic villous sampling, foetal blood sampling, embryo reduction, shunt insertion, external cephalic version, manual removal of the placenta, and caesarean section [9]. Most sensitization cases take place at birth [10] and rarely affect the first pregnancy [10]. Isoimmunization may lead to adverse maternal and foetal/neonatal outcomes such as hypertensive disease of the newborn (HDN) [11]. Mild jaundice, anaemia, and hydrops fetalis are the main signs of HDN. Extra medullary haematopoiesis (due to anaemia) may result in hepatosplenomegaly with resultant risks during labour and delivery, such as asphyxia and splenic rupture. In the post-natal period, the neonate may develop jaundice, anaemia, hypoglycaemia, difficulty in breathing, or death [11]. The laboratory findings vary with the severity of HDN and may include: hyperbilirubinemia, reticulocytosis, elevated nucleated RBC count, thrombocytopenia, leukopenia, hypoalbuminemia, and RhD-ve blood type [12]. RhD-ve has been associated with the development of pre-eclampsia, placental abruption, cesarean delivery due to non-reassuring foetal status [13], oligohydramnios, and polyhydramnios [14].

Despite the availability of anti-D prophylaxis to prevent sensitization, gaps in its uptake, timing, and follow-up remain in many low- and middle-income countries. There is limited local data on the burden, risk factors, and pregnancy outcomes associated with Rh isoimmunization in Kenya, which hinders the formulation of effective management protocols and prevention strategies. This study aimed to determine the prevalence, sociodemographic characteristics, and pregnancy outcomes of rhesus isoimmunized women managed at the Kenyatta National Hospital.

Methods     

Study design and setting: this cross-sectional study was conducted at Kenyatta National Hospital, a teaching and referral facility in East and Central Africa. The Department of Obstetrics and Gynaecology manages about 1,200 antenatal clients and 2,000 deliveries monthly.

Study population: the study included RhD-negative women attending ANC between January 2013 and December 2019. Of 216 records reviewed, 194 with complete data were analysed. Inclusion criteria were complete records of RhD-negative women with delivery details; files with missing data were excluded.

Data collection: data was extracted using a structured tool. At booking, all women undergo ABO and RhD typing. RhD-negative mothers receive anti-D immunoglobulin (300 μg) between 28-34 weeks and postpartum if the baby is RhD-positive. Information on demographics, clinical history, and outcomes was retrieved from hospital records.

Definitions: rhesus isoimmunization was defined as the presence of maternal anti-D antibodies. Outcomes included anaemia, antepartum haemorrhage, hydrops fetalis, IUFD, birth weight <2500 g, APGAR <7, and Neonatal Intensive Care Unit (NICU) admission.

Statistical analysis: data was analysed using SPSS v23. Descriptive statistics summarized characteristics. Fisher´s exact test assessed associations between isoimmunization and outcomes. Significant variables (p<0.05) were entered into multivariable logistic regression to generate adjusted odds ratios (aORs), 95% CIs, and p values.

Ethical considerations: ethical approval was obtained from the KNH-University of Nairobi (UoN) Ethics and Research Committee (Ref: KNH-ERC/A/124). Patient confidentiality was maintained, and identifiers were omitted (Figure 1).

Results     

General characteristics of the study population: a total of 194 mothers were assessed, of whom 8 (4.1%) had rhesus isoimmunization. Most participants (53.6%) were aged 25-35 years, 27.8% were 19-24 years, and 18.6% were 36-49 years. Nearly half (49%) had attained secondary education, 38.7% tertiary, and 12.3% primary education. The majority were married (91.2%) and multigravida (69.1%) (Table 1).

Regarding blood group, 41.8% were O-negative, 33.5% A-negative, 19.6% B-negative, and 2.1% AB-negative. Partner blood group was documented for 30 participants; most were B-positive (73%) (Table 2).

Maternal factors and isoimmunization: among women with isoimmunization, 75% had experienced a prior pregnancy loss, with none documented as having received anti-D prophylaxis after the loss. Positive ICT titres were recorded in 87.5% of isoimmunized women. Isoimmunization was significantly associated with prior miscarriage (62.5% vs 16.7% in non-isoimmunized; p=0.006). Other maternal factors, including anemia (p=0.239), cesarean delivery (p=0.263), and antepartum hemorrhage (p=0.226), were not statistically associated with isoimmunization (Table 3).

Fetal and neonatal outcomes: isoimmunization was strongly associated with adverse fetal and neonatal outcomes. Hydrops fetalis occurred in 37.5% of isoimmunized pregnancies versus 0.5% of non-isoimmunized (p<0.001), while intrauterine fetal demise (IUFD) was reported in 62.5% versus 1.6% (p<0.001). Isoimmunized women were more likely to deliver prematurely and have infants with birth weight <2500g (85.5% vs 4.3%), poor APGAR scores (75% vs 2.2%), and NICU admission (37.5% vs 2.7%), all p<0.001 except NICU (p=0.002).

Discussion     

This study aimed to determine the prevalence of rhesus iso-immunization among Rh-negative pregnant women and assess associated maternal and fetal outcomes. Among the 194 women assessed, the prevalence of rhesus iso-immunization was 4.1%, comparable to 5.5% reported by Adeyemi et al. in Ogbomosho, Nigeria, but lower than the 9.1% observed in Kaduna, Nigeria [15]. Routine antenatal prophylaxis has been reported to reduce the risk of sensitization to as low as 0.2% [2]. In our study, iso-immunized women were more likely to experience adverse maternal outcomes such as miscarriage (62.5% vs 16.7%, p=0.006), though differences in cesarean delivery, antepartum hemorrhage, and mild anemia were not statistically significant (p>0.05). These findings are consistent with previous studies showing that iso-immunization increases the risk of complications during pregnancy and postpartum [4,14,16].

Fetal complications were markedly higher among isoimmunized women. Hydrops fetalis occurred in 37.5% of isoimmunized pregnancies compared to 0.5% in the non-iso-immunized group. Similarly, intrauterine fetal demise was reported in 62.5% versus 1.6% (p<0.001). These rates exceed those reported in Bangladesh, where fetal death among iso-immunized women was 14% [17]. The elevated rates in our cohort reflect limited early fetal surveillance and a lack of intrauterine interventions for high-risk pregnancies.

Neonatal outcomes were also significantly worse among infants born to iso-immunized mothers. Low birth weight (<2500g) occurred in 85.5% versus 4.3% of non-isoimmunized pregnancies (p<0.001), poor APGAR scores in 75% versus 2.2% (p<0.001), and NICU admission in 37.5% versus 2.7% (p=0.002). Similar trends were reported in Nigeria, where 31.4% of neonates in the iso-immunized group had poor APGAR scores and required NICU admission [8]. The higher proportions in this study, partly explained by the small number of iso-immunized women, emphasize the need for targeted interventions to monitor and manage high-risk pregnancies among Rh-negative women.

The findings of this study have important clinical and public health implications. They show the need for routine antenatal anti-D prophylaxis, early identification of Rh-negative women, and enhanced fetal monitoring to prevent alloimmunization and reduce adverse outcomes. Moreover, our results highlight the importance of documenting partner blood group and prior pregnancy history, which are crucial for risk stratification and management planning.

The study is limited by its retrospective design, which is prone to gaps in documentation. Additionally, the low number of women with isoimmunization limited statistical power, and the use of Fisher´s exact test may be conservative, potentially underestimating associations. Consequently, we could not perform more robust correlation analyses between maternal and neonatal outcomes. Despite these limitations, the study provides valuable insights into maternal and fetal risks associated with rhesus iso-immunization in this setting and supports the implementation of targeted prophylaxis and monitoring strategies.

Conclusion     

Rh-negative pregnancies represent an important subgroup of the obstetric population at KNH, with a prevalence of rhesus iso-immunization of 4.1%. Although the number of iso-immunized women was low, they experienced significantly higher rates of adverse maternal and fetal outcomes, including miscarriages, hydrops fetalis, intrauterine fetal demise, low birth weight, poor APGAR scores, and increased NICU admissions compared to non-iso-immunized women. These findings highlight the clinical importance of early identification of Rh-negative women, routine antenatal anti-D prophylaxis, and enhanced fetal surveillance to reduce sensitization and improve maternal and neonatal outcomes in this high-risk population.

Competing interests     

The authors declare no competing interests.

Authors' contributions     

Conception and study design: John Abayo Otieno, Rose Jepchumba Kosgei, and Omondi Ogutu; data collection: John Abayo Otieno, Chrisostim Wekesa Barasa, and Rose Betty Mukii; data analysis and interpretation: Chrisostim Wekesa Barasa and Rose Betty Mukii; manuscript drafting: John Abayo Otieno, Rose Jepchumba Kosgei, Omondi Ogutu, Chrisostim Wekesa Barasa, and Rose Betty Mukii; manuscript revision: John Abayo Otieno, Chrisostim Wekesa Barasa, and Rose Betty Mukii; guarantor of the study: John Abayo Otieno. All the authors read and approved the final version of this manuscript.

Acknowledgments     

We appreciate the efforts of all our research assistants who worked tirelessly to collect the data; you have been of great help. We thank the patients who consented and allowed us to carry out the study seamlessly.

Tables and figure     

Table 1: characteristics of the rhesus-negative women who attended the antenatal clinic at the Kenyatta National Hospital between January 2013 and December 2019

Table 2: blood group types for the rhesus-negative and the partners who attended the antenatal clinic at the Kenyatta National Hospital

Table 3: adverse maternal and foetal outcomes among rhesus-negative women at the Kenyatta National Hospital, between January 2013 and December 2019

Figure 1: study flow diagram

References