Consequences of being Rhesus D immunized during pregnancy and how to optimize new prevention strategies

Does high body mass index (>25 kg/m2) or weight (>80 kg) reduce the effectiveness of anti-D prophylaxis in Rh(D)-negative pregnant women? A systematic review and meta-analysis

BACKGROUND AND OBJECTIVES

Haemolytic disease of the foetus and newborn (HDFN) occurs when maternal antibodies, often triggered by foetal antigens, destroy foetal and neonatal red blood cells. Factors like antibody strength, quantity and gestational age influence HDFN severity. Routine antenatal anti-D prophylaxis (RAADP) has significantly reduced HDFN cases. However, the effect of overweight/obesity (body mass index [BMI] > 25/30 kg/m2) on anti-D prophylaxis efficacy remains unclear. This systematic review will examine the impact of BMI on anti D prophylaxis effectiveness in Rh(D) negative pregnant women.

MATERIALS AND METHODS

We conducted a systematic review and meta-analysis following Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) protocols. We searched databases from 1996 to 2023, focusing on studies exploring the link between high BMI/weight and anti-D serum levels in Rh(D)-negative pregnant women with Rh(D)-positive foetuses. Ten eligible studies were included, three suitable for meta-analysis. Study quality was assessed using the Strengthening the Reporting Observation Studies in Epidemiology (STROBE) checklist. Statistical analyses included Pearson correlation coefficients and risk differences.

RESULTS

Our meta-analysis revealed a significant negative correlation (r = -0.59, 95% confidence interval [CI]: -0.83 to -0.35, p = 0.007) between high BMI/weight and serial anti-D levels in in Rh(D)-negative pregnant women with Rh(D)-positive foetuses. High BMI/weight had lower odds of serial anti-D level exceeding 30 ng/mL (arcsine risk difference [ARD] = 0.376, 95% CI: 0.143-0.610, p = 0.002). Heterogeneity among studies was low (I2 = 0).

CONCLUSION

While our analysis suggests a potential linkage between high BMI/weight and reduced efficacy of anti-D prophylaxis, caution is warranted due to study limitations. Variability in study design and confounding factors necessitate careful interpretation. Further research is needed to confirm these findings and refine clinical recommendations.

Hemolytic disease of the fetus and newborn-a perspective of immunohematology

BACKGROUND

Hemolytic disease of the fetus and newborn is a public health problem caused by maternal-fetal incompatibility; no prophylaxis is available for most alloantibodies that induce this disease. This study reviews the literature regarding which antibodies are the most common in maternal plasma and which were involved in hemolytic disease of the fetus and newborn.

METHOD

Seventy-five studies were included in this review using a systematic search. Two independent authors identified studies of interest from the PubMed and SciELO databases.

MAIN RESULTS

Forty-four case reports were identified, of which 11 babies evolved to death. From 17 prevalence studies, the alloimmunization rate was 0.17 % with 161 babies receiving intrauterine transfusions and 23 receiving transfusions after birth. From 28 studies with alloimmunized pregnant women (7616 women), 455 babies received intrauterine transfusions and 21 received transfusions after birth.

CONCLUSION

Rh, Kell, and MNS were the commonest blood systems involved. The geographical distribution of studies shows that as these figures vary between continents, more studies should be performed in different countries. Investing in early diagnosis is important to manage the risks and complications of hemolytic disease of the fetus and newborn.

Disease severity in subsequent pregnancies with RhD immunization: A nationwide cohort

BACKGROUND AND OBJECTIVES

To evaluate the severity of haemolytic disease of the foetus and newborn (HDFN) in subsequent pregnancies with RhD immunization and to identify predictive factors for severe disease.

MATERIALS AND METHODS

Nationwide prospective cohort study, including all pregnant women with RhD antibodies. All women with at least two pregnancies with RhD antibodies and RhD-positive foetuses were selected. The main outcome measure was the severity of HDFN in the first and subsequent pregnancy at risk. A subgroup analysis was performed for the group of women where RhD antibodies developed after giving birth to an RhD-positive child and thus after receiving anti-D at least twice (group A) or during the first pregnancy at risk for immunization (group B).

RESULTS

Sixty-two RhD immunized women with a total of 150 RhD-positive children were included. The severity of HDFN increased for the whole group significantly in the subsequent pregnancy (p < 0.001), although it remained equal or even decreased in 44% of women. When antibodies were already detected at first trimester screening in the first immunized pregnancy, after giving birth to an RhD-positive child (group A), severe HDFN in the next pregnancy was uncommon (22%). Especially when no therapy or only non-intensive phototherapy was indicated during the first immunized pregnancy (6%) or if the antibody-dependent cell-mediated cytotoxicity result remained <10%. Contrarily, women with a negative first trimester screening and RhD antibodies detected later during the first pregnancy of an RhD-positive child (group B), often before they had ever received anti-D prophylaxis, were most prone for severe disease in a subsequent pregnancy (48%).

CONCLUSION

RhD-mediated HDFN in a subsequent pregnancy is generally more severe than in the first pregnancy at risk and can be estimated using moment of antibody detection and severity in the first immunized pregnancy. Women developing antibodies in their first pregnancy of an RhD-positive child are at highest risk of severe disease in the next pregnancy.

Plasma level of mannose-binding lectin is associated with the risk of recurrent pregnancy loss but not pregnancy outcome after the diagnosis

STUDY QUESTION

Are low or high plasma mannose-binding lectin (p-MBL) levels associated with recurrent pregnancy loss (RPL) and the reproductive and perinatal outcomes before and after RPL?

SUMMARY ANSWER

The prevalence of low p-MBL levels was significantly higher in RPL patients, while high levels were significantly less prevalent. No association was found between p-MBL level and reproductive and perinatal outcomes before and after RPL.

WHAT IS KNOWN ALREADY

Mannose-binding lectin (MBL) is an important component in the innate immune system. Low p-MBL levels have been associated with RPL, while the correlation with high levels has been poorly studied. Adverse perinatal outcomes are generally more frequent among RPL patients, but reports concerning the association between maternal p-MBL levels and perinatal outcomes, including birth weight (BW) and gestational age (GA), are conflicting.

STUDY DESIGN, SIZE, DURATION

This study was a combined cross-sectional and cohort study of 267 RPL patients admitted to the RPL Center of Western Denmark between January 2016 and March 2020. RPL patients were followed until birth of a liveborn child or until end of follow-up, March 2021. A sample of 185 healthy female blood donors of reproductive age was used as a MBL reference group.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All RPL patients had ≥3 consecutive pregnancy losses, a regular menstrual cycle and no known significant chromosomal or uterine malformations. At the first consultation, routine blood samples including p-MBL measurement and detailed obstetrical and perinatal information were collected. p-MBL levels in RPL patients were compared to the MBL reference group. A logistic regression analysis adjusted for relevant confounders assessed the association between low p-MBL levels and an unsuccessful reproductive outcome in RPL patients in first pregnancy after admission. Perinatal outcomes before and after RPL were compared between RPL subgroups according to low (≤500 µg/l), intermediate (501–3000 µg/l) and high (>3000 µg/l) p-MBL levels.

MAIN RESULTS AND THE ROLE OF CHANCE

Significantly more RPL patients had low p-MBL levels (prevalence proportion ratio (PPR): 1.79, 95% CI: 1.34–2.38) and fewer had high p-MBL levels (PPR: 0.56, 95% CI: 0.40–0.79) compared to the reference group, while the prevalence of intermediate p-MBL level was not different between the groups (PPR: 0.86, 95% CI: 0.69–1.08). In the prospective study, low p-MBL level was not a significant risk factor for a pregnancy loss in the first pregnancy after admission after adjustment for age, BMI and smoking. Neither before nor after the RPL diagnosis were maternal p-MBL levels significantly associated with BW or GA.

LIMITATIONS, REASONS FOR CAUTION

Only 161 (60.3%) patients had given birth after RPL during the follow-up period, which limited the possibility to detect clear associations between p-MBL levels and perinatal outcomes after RPL.

WIDER IMPLICATIONS OF THE FINDINGS

In agreement with several previous studies, low p-MBL levels are strongly associated with RPL, while this study for the first time documents that high levels may play a protective role, which suggests a causal relationship. We suggest that larger prospective studies evaluate the association between p-MBL levels and RPL prognosis.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was received. We acknowledge the Department of Obstetrics and Gynaecology at Aalborg University Hospital for financial support. U.S.K. has reported personal fees from Merck, consulting fees from IBSA Nordic, and a grant from Gedeon Richter, Merck and IBSA Nordic outside of the submitted work.

TRIAL REGISTRATION NUMBER

ID from clinicaltrials.gov is NCT04017754.

Management and clinical consequences of red blood cell antibodies in pregnancy: A population-based cohort study

INTRODUCTION

Anti-D alloimmunization is the most common cause of severe hemolytic disease of the fetus and newborn (HDFN). The management of pregnancies affected by less frequent red blood cell (RBC) antibodies poses a challenge to clinicians, and perinatal outcomes are less well described. This study aimed to describe the frequency of clinically significant RBC antibodies in our pregnant population and analyze the risk of prenatal and postnatal treatment for HDFN in relation to our national risk classification system and management guidelines.

MATERIAL AND METHODS

A retrospective cohort study in the population of all alloimmunized singleton pregnancies in the Stockholm region 1990-2016. Descriptive summaries of different RBC antibodies and pregnancy outcomes were presented, the risks of intrauterine blood transfusion (IUT) and neonatal treatment for HDFN were estimated by type of antibodies.

RESULTS

Of the 1724 alloimmunized pregnancies, 1079 (63%) were at risk of HDFN and constituted our study cohort. Anti-D was detected in 492 (46%) pregnancies, followed by anti-E in 161 (15%), and anti-c in 128 (12%). Eighty-seven (8%) pregnancies had IUT, with the highest risk in pregnancies affected by anti-D combined with other antibodies. The maximum titer recorded before IUT was 64 or above, except for two pregnancies affected by anti-c, for which the maximum titers were 8 and 16. For the 942 (95%) live-born neonates from 992 alloimmunized pregnancies without IUT, the median gestational age at birth was 38⁺⁵  weeks compared with 35⁺⁵  weeks for those who had IUT. Neonatal treatment was most common in the anti-D alone and anti-D combined groups, with 136 (57%) and 21 (44%), respectively, treated with phototherapy and 35 (15%) and 9 (20%) receiving exchange transfusions, respectively. For pregnancies complicated by moderate- and low-risk antibodies, phototherapy was less frequent (32 [36%] and 21 [19%]) and exchange transfusion was rare (5 [6%] and 3 [3%]).

CONCLUSIONS

Anti-D, especially in combination with other antibodies, presents the highest risk of severe HDFN. The classification of less frequent and less well-known RBC antibodies into risk groups can help clinicians in assessing the risk of HDFN and counseling alloimmunized pregnant women regarding the risk of prenatal and postnatal treatments.

Time points and risk factors for RhD immunizations after the implementation of targeted routine antenatal anti-D prophylaxis: A retrospective nationwide cohort study

INTRODUCTION

Targeted routine antenatal anti-D prophylaxis was introduced to the national prophylaxis program in Finland in late 2013. The aim of this study was to assess the incidence, time-points, and risk factors for Rhesus D immunization after the implementation of routine antenatal anti-D prophylaxis, in all women in Finland with antenatal anti-D antibodies detected in 2014-2017.

MATERIAL AND METHODS

In a nationwide population-based retrospective cohort study, the incidence, time-points, and risk factors of anti-D immunizations were analyzed. Information on antenatal screening was obtained from the Finnish Red Cross Blood Service database, and obstetric data from hospital records and the Finnish Medical Birth Register.

RESULTS

The study included a total of 228 women (197 with complete data for all pregnancies). After the implementation of routine antenatal anti-D prophylaxis, the prevalence of pregnancies with anti-D antibodies decreased from 1.52% in 2014 to 0.88% in 2017, and the corresponding incidence of new immunizations decreased from 0.33% to 0.10%. Time-points for detection of new anti-D antibodies before and after 2014 were the first screening sample at 8-12 weeks of gestation in 52% versus 19%, the second sample at 24-26 weeks in 20% versus 50%, and the third screening at 36 weeks in 28% versus 32%.

CONCLUSIONS

The incidence of new anti-D immunizations decreased as expected after the implementation of routine antenatal anti-D prophylaxis. True failures are rare and they mainly occur when the prophylaxis is not given appropriately, suggesting a need for constant education of healthcare professionals on the subject.

G6PD Deficiency Prevalence as a Cause of Neonatal Jaundice in a Neonatal Ward in Dohuk, Iraq

OBJECTIVE

The current study initiated to address the effect of glucose-6-phosphate dehydrogenase (G6PD) deficiency on the pathogenesis and the severity of neonatal hyperbilirubinemia (NHB).

STUDY DESIGN

A total of 100 newborns with moderate to severe indirect hyperbilirubinemia and 50 normal neonates without hyperbilirubinemia had been enrolled in the current case-control study. All enrolled neonates had been tested for ABO and Rh(D) blood grouping, Total serum bilirubin measurement, complete blood count, morphology, reticulocyte counts, direct Coombs' test, and G6PD enzyme assay.

RESULTS

From all enrolled hyperbilirubinemic neonates, 16% were G6PD deficient and this displays a statistically significant difference in comparison to controls (only 6% were G6PD deficient). Also, significant difference was found in the level of serum indirect bilirubin among G6PD-deficient neonate in comparison to G6PD nondeficient neonates which had contributed significantly to the difference in the duration of phototherapy and hospitalization among deficient neonate. Despite this, no significant difference found in the onset of presentation, reticulocytes count, and age of neonates between the two groups (G6PD-deficient and G6PD nondeficient neonates).

CONCLUSION

The current study augments the etiological role of G6PD in the causation and severity of NHB in the region; however, in the absence of significant difference in the reticulocytes and the hemoglobin level, the underlying mechanism cannot be backed to the excess hemolysis alone.

Altered strategy of prophylactic anti-D administration in pregnancy to cover term and post-term - a pilot study

BACKGROUND AND OBJECTIVE

Routine antenatal anti-D prophylaxis (RAADP) to RhD-negative women is most often administered in gestational age (GA) 28-30 weeks with the next anti-D dose administered postpartum. The aim of this study was to analyse the proportion of RhD-negative women where RAADP is not detectable at term and in a pilot study to investigate whether RAADP administered in GA 28 and 38 results in detectable levels at term, post-term and post-delivery.

MATERIALS AND METHODS

In a retrospective analysis, 4280 RhD-negative women carrying an RHD positive fetus were included and the proportion with a negative antibody screen at delivery was determined. In the second part, 39 pregnancies were included prospectively, a second dose of RAADP was administered in GA 38 weeks, and anti-D was quantified before the second dose and then weekly for 5 weeks.

RESULTS

In the retrospective analysis, 20·5% (856/4280) with RAADP administered in GA 28 were negative in routine antibody screening at delivery. In the small prospective study, 18% (7/39) had a negative antibody screen and 26% (10/39) had levels below 0·005 IU/ml, in the quantification assay, in GA 38. Anti-D prophylaxis administered in GA 38 showed detectable levels of anti-D up to 30 days post-delivery, with concentration at delivery 0·060 ± 0·034 IU/ml (mean ± SD).

CONCLUSION

Approximately 20% of the RhD-negative women show non-detectable levels of anti-D at term. A second dose of RAADP at GA 38 results in stable concentrations of anti-D at term, post-term and post-delivery, but with large interindividual variation.

Rhesus D alloimmunization in pregnancy from 1996 to 2015 in Iceland: a nation-wide population study prior to routine antenatal anti-D prophylaxis

BACKGROUND

Rhesus D (RhD) incompatibility is still the most important cause of hemolytic disease of the fetus and newborn (HDFN) worldwide. The aim of this study was to investigate the incidence, causes, and consequences of anti-D alloimmunizations in pregnancy in Iceland, prior to implementation of targeted routine antenatal anti-D prophylaxis (RAADP) in 2018.

STUDY DESIGN AND METHODS

This was a nation-wide cohort study of 130 pregnancies affected by RhD alloimmunization in Iceland in the period from 1996 through 2015. Data were collected from transfusion medicine databases, medical records, and the Icelandic Medical Birth Register.

RESULTS

Of 130 RhD alloimmunizations, 80 cases (61.5%) represented new RhD immunization in the current pregnancy. Sensitization was discovered in the third trimester in 41 (51.3%) and occurred in the first pregnancy in 14 cases (17.5%). The most likely causative immunization event was the index pregnancy for 45 (56.25%), a previous pregnancy/birth for 26 (32.5%), abortion for 3 (3.75%), and unknown for 6 women (7.5%). Higher anti-D titers were associated with shorter gestational length, cesarean sections, positive direct antiglobulin test (DAT), and severe HDFN. Intrauterine transfusion (IUT) was performed in five pregnancies (3.8%), and 35 of 132 (26.5%) live-born neonates received treatment for HDFN; 32 received phototherapy (24.2%), 13 exchange transfusion (9.8%), and seven simple blood transfusion (5.3%).

CONCLUSION

In about half of cases, RhD alloimmunization was caused by the index pregnancy and discovered in the third trimester. Thus, the newly implemented RAADP protocol should be effective in reducing the incidence of RhD immunization in Iceland in the future.

Anti-D quantification in relation to anti-D titre, middle cerebral artery Doppler measurement and clinical outcome in RhD-immunized pregnancies

BACKGROUND

The optimal strategy to monitor RhD-immunized pregnancies is not evident. Whether a quantitative analysis of anti-D antibodies adds valuable information to anti-D titre is unclear. The aim of this study was to evaluate the relevance of anti-D quantification in routine monitoring of RhD-immunized pregnancies.

MATERIALS AND METHODS

In a retrospective study, 64 consecutive pregnancies in 61 immunized women with anti-D titre ≥128 at any time during pregnancy were included. According to routine, at titre ≥128, anti-D quantification was performed by flow cytometry and the peak systolic velocity in the middle cerebral artery was measured by ultrasound. Decisions for treatment with intrauterine blood transfusion were based on increased peak systolic velocity in the middle cerebral artery.

RESULTS

Increasing anti-D concentrations correlated well to increasing anti-D titres, but at each titre value, there was a large interindividual variation, in the determined anti-D concentration. Intrauterine transfusions were initiated in 35 pregnancies according to algorithms based on ultrasound measurements, at anti-D concentrations of 2·4-619 IU/ml and titre 128-16 000. Sixty pregnancies resulted in a live-born child, three in miscarriage and one in termination of pregnancy. During the perinatal care in the neonatal intensive care unit, thirty-one of the neonates were treated with blood exchange transfusions and/or red cell transfusions and 47 were treated with phototherapy.

CONCLUSION

Anti-D quantification does not add further information compared to anti-D titre, in defining a critical level to start monitoring RhD-immunized pregnancies with Doppler ultrasound.

Associations of Rhesus and non-Rhesus maternal red blood cell alloimmunization with stillbirth and preterm birth

BACKGROUND

Although the risks of adverse pregnancy outcomes associated with anti-D antibodies are well-recognized, much less is known concerning alloimmunization with other red blood cell antibodies detected during routine maternal screening. To date, most reports of adverse pregnancy outcomes associated with non-anti-D antibodies have been from small case studies. The aim of this study was to examine the associations of maternal alloimmunization with specific red blood cell antibodies and the risks of preterm birth and stillbirth in the Swedish population.

METHODS

All antibody screening, outcome and covariate data were obtained through linkages of Swedish national health and data registers. Follow-up in these population-based registers was available up to 31 December 2002. The final study sample consisted of 1,022,569 singleton births from 668,952 mothers during 1987-2002.

RESULTS

In total, 1.3% of the 1,022,569 study pregnancies were alloimmunized. In adjusted logistic regression models, compared with having no antibodies, alloimmunization with anti-D, anti-E, anti-C and anti-c was associated with increased risk of both stillbirth and preterm birth. In addition, anti-Kell was associated with increased risk of preterm birth and anti-Lea with increased risk of stillbirth. Compared with firstborn children, risk of preterm birth associated with alloimmunization was greater in subsequent births

CONCLUSIONS

In the largest study to date, alloimmunization with Rhesus, K- and -Lea red blood cell antibodies increased the risk of preterm birth and/or stillbirth. The association of anti-Lea with stillbirth was an unexpected finding. Further study of the consequences of non-anti-D alloimmunization is warranted.