Fetal treatment and long-term neonatal outcomes in severe maternal red cell alloimmunization – a single-centre experience

Introduction

Haemolytic disease of the fetus and the newborn (HDFN) occurs due to maternal immunoglobulin G (Ig G) alloantibodies that actively cross the placenta and bind to paternally derived fetal antigens on the erythrocytes. The most commonly implicated antigens are D, followed by K, c and E [1]. Antibody-coated erythrocytes are haemolyzed in the fetal spleen potentially resulting in fetal anemia. Compensatory erythropoiesis is stimulated and fetal cardiac output increases in response to hypoxemia [2]. The fetal circulation becomes hyperdynamic, which can lead to the development of cardiomegaly, hydrops and finally intrauterine fetal demise (IUFD) can occur without timely detection and treatment [3]. After birth, the immature neonatal liver is unable to conjugate increased levels of bilirubin, which is deposited in the neonatal tissues, including the central nervous system, particularly the basal ganglia and brainstem nuclei, potentially leading to bilirubin encephalopathy. Chronic bilirubin encephalopathy involves psychomotor handicap, athetoid cerebral palsy and hearing problems and is an important cause of severe long-term morbidity [4].

Even though no specific cure for HDFN exists, its incidence, especially in high-income countries, has dramatically decreased due to preventative efforts such as screening of all pregnancies for RhD status, subsequent Rhesus immunoprophylaxis administration and transfusions of RhD matched and Kell negative blood products to women of child-bearing age. The rate of RhD alloimmunization is currently 0.3–0.6 % in developed countries [5]. Nevertheless, HDFN has not yet been eradicated.

Owing to the improvement of fetal and postnatal management strategies, the outcome of affected pregnancies is generally good. Through enhanced surveillance of high-risk pregnancies we can timely detect fetal anemia [6]. Standard therapy for fetal anemia is intrauterine transfusion (IUT) which improves fetal haemoglobin levels, reverts hydrops and prolongues the duration of pregnancy, and consequently markedly improves the outcome [7], [8], [9]. In severe maternal red blood cell (RBC) alloimmunization, several adjunctive fetal therapy strategies exist to postpone the need for IUT beyond 20 gestational weeks such as intravenous immunoglobulins (IVIg) alone or in combination with therapeutic plasmapheresis (TPE) [10], [11], [12]. After birth hyperbilirubinemia may be treated with phototherapy and in severe cases with exchange transfusions (ET). Anemia due to haemolysis or inhibition of erythropoiesis may be treated with red blood cell transfusions or erythropoietin [13]. Phototherapy is of extreme importance to diminish the possibility of bilirubin encephalopathy [14].

Due to the rarity of HDFN, and numerous treatment options, it is crucial to evaluate and report upon the management of affected pregnancies and newborns. We therefore aimed to describe the Slovenian cohort of patients with HDFN, who required fetal treatment, to review fetal treatment strategies and to describe pregnancy and long-term neurodevelopmental outcomes.

Materials and methods

This retrospective single-centre cohort study was conducted at the Department of Perinatology of the University Medical Centre (UMC) Ljubljana, which is the referral institution for the management of the most complicated perinatal pathologies, including HDFN. Slovenia has a population of two million and approximately 18,000 children are born annually [15].

Our institution was one of the 31 centres from 22 countries that have taken part in a worldwide multicentric cohort study DIONYSUS (worlDwIde cOllaboratioN for hemolYtic diSease of the fetUs and newborn) on antenatal and postnatal management practice variations in HDFN between 2006 and 2021.

Perinatal and neonatal data were collected from the medical records: hospital’s informational system Hipokrat© and archived medical files. Data regarding type of alloimmunization, titre and ADCC values were provided by the Blood Transfusion Centre of Slovenia. Primary care paediatricians were contacted by a member of our team to gather information about neurodevelopmental progress at the corrected age of two years. The tests performed at the corrected age of two years were not standardised as no specific guidelines exist.

Maternal information included demographics, previous pregnancy outcomes, and RBC transfusion data (blood group, antibody specificity, serological titre, ADCC values, previous transfusions). For women who appeared more than once in the database, each alloimmunized pregnancy was recorded as a separate event.

Antenatal data included gestational age at the first detection of antibodies, type of antibodies, titres, ADCC values, abnormal ultrasound findings, type of fetal treatment, gestational age at the start and stop of fetal treatment, IUT characteristics, fetal laboratory values before and after each IUT, complications following IUTs. Neonatal data included timing and mode of delivery, birth weight, Apgar scores, laboratory results, postnatal management strategies.

Outcome measures included fetal and neonatal survival, complications of fetal treatment, adverse neonatal outcomes, and neurodevelopmental status at the corrected age of 2 years. Adverse neonatal outcomes included the need for respiratory support and severe neonatal morbidity, defined as sepsis with a positive blood culture, necrotising enterocolitis (NEC) ≥Bell stage 2A and the presence of severe cerebral injury (SCI). SCI was defined as periventricular leukomalacia (PVL) grade 2 or more, intraventricular haemorrhage (IVH) grade 3 or more, ventriculomegaly, arterial, or venous infarct or presence of porencephalic or parenchymal cysts.

No national guidelines exist on the management of DHDFN in Slovenia. Until 2023 the management was guided by the American Academy of Pediatrics (AAP). Currently, neonatologists are following the National Institute for Health and Care Excellence (NICE) Guidelines. IVIg are not used routinely and are used in rare circumstance when ET is not possible, such as inability to transport the newborn into the referral center or lack of blood products. Newborns undergo Auditory Brainstem Response testing and if deemed pathological, Brainstem Evoked Auditory Potential Testing is also performed. Children are followed up in the outpatient developmental clinics for at least 2 years.

Case series presentation

Discussion

This is the first study describing severe cases of HDFN requiring fetal treatment at our institution, which is the only fetal therapy centre in Slovenia. This article includes all cases of severe HDFN over a 16-year period across the country and describes the fetal and postnatal management at a national level.

Despite the wide-spread use of anti-D immunoglobulins for the prevention of alloimmunization in our country, by far the most commonly implicated antigen in severe HDFN was RhD (12/16, 75.0 %). Like in our study, RhD was identified as the causative antigen in 71.6 % of cases reported by Pan et al. [16]. Our results highlight the importance of avoiding transfusion mistakes as well as the importance of prophylactic use of the anti-D immunoglobulins in case of potentially sensitising events which should never be forgotten.

Several fetal therapy centres alternatively use IVIg and TPE in severe maternal RBC alloimmunization to delay the onset of fetal anemia, for example high antibody titres, high ADCC values, or in mothers with unfavourable obstetric history (such as IUFD due to HDFN in the previous pregnancy). In the largest study from the 1990s, starting IVIg therapy before 21 weeks of gestation, followed by IUTs after 20 weeks appeared to reduce fetal mortality from 20 to 15 % [17]. In a multicentre PETIT study, IVIg was associated with a reduced risk of hydrops and the need for ET compared with the untreated group [10]. IVIg treatment, when started before 13 weeks of gestation, demonstrated a potential to delay the need for IUT in comparison to the previous pregnancy. However, the overall infant survival in the PETIT study was high, 88 %, but did not differ between the IVIg-treated and untreated groups. As in our cases, a combined treatment with TPE and IVIg early in pregnancy and IUT later in pregnancy, if needed, was reported to be successful in the management of severe maternal RBC alloimmunization in case reports [11], 18], 19].

One of our patients with RhD and RhC alloimmunization received 5 doses of IVIg from 18 weeks until 23 weeks without the need for subsequent IUTs and a healthy boy was born at 36 3/7 without sequelae, which highlights the potential efficacy of IVIg. The decision for the use of IVIg was based on the high titres and ADCC in the first trimester and a history of fetal death at 18 weeks of pregnancy in her previous pregnancy (her third and the second pregnancy with alloimmunization) with no cause of death identified. In another case we opted for IVIg applications starting from week 10 due to previous IUFD of a severely anemic fetus at 29+4 weeks due to RhD alloimmunization as a consequence of RhD positive blood products. After 20 weeks we continued with TPEs and 9 IUTs. A healthy girl was born vaginally at 36 3/7 and has no neurodevelopmental delay at the age of 4 years. Despite promising results of alternative treatment options of severe maternal RBC alloimmunization from retrospective studies and case reports, we still lack evidence from randomized controlled trials to prove the efficacy of IVIg and TPE and the decision for alternative fetal treatment options remains individualized.

Among 71 IUTs performed in our institution in the observed period, the rate of severe adverse events was 7 %, which is comparable to larger centres. Importantly, there were no cases of bleeding from the puncture site or infections and only one case of PPROM, followed by a preterm delivery, which are commonly described complications of IUT [16], 20].

Outcomes of the fetal treatment for severe HDFN in our cohort are favourable. The overall survival rate was 89.5 %. No neonatal deaths occurred, which is in line with the literature [20]. Neonatal outcomes in our cohort are also comparable to international data. All but one newborn had an Apgar score of more than 7 after 5 min and none of them was hydropic at the time of delivery. Most children were born in the late preterm period (75.0 %), unfortunately, none were born after 37 weeks of gestation. According to a systematic review by de Winter et al. [2], most children with HDFN are born in the late preterm period, around 35 weeks’ gestation. In the future we should avoid delivering neonates in the late preterm period and aim for delivery after 37 weeks with the last IUT being around 35 weeks. Late preterm babies are at higher risk of complications than full-term babies, such as respiratory distress, temperature instability, hypoglycaemia, jaudnice, feeding difficulties, apnea, sepsis and they carry and increased risk of long-term morbidities, such as neurodevelopmental delay, cerebral palsy, chronic respiratory and metabolic disease [21].

Most newborns received the postnatal care for HDFN (93.8 %), with only four cases requiring ET (25.0 %), which is in line with literature data and is not a reflection of unsatisfactory fetal management [16]. There were no neonatal deaths in our cohort, highlighting quality postnatal care at our institution.

Neurodevelopmental outcome is often lacking in research on rare diseases. In this study, we were able to assess it. One child was classified as having moderate neurodevelopmental delay at the corrected age of 2 years without the requirement of special needs education. Interestingly, the sensitising antigen was RhE, which has been described as a rare cause for severe HDFN [22] and the highest titre was 64 with ADCC of 10 %. She was, however, born prematurely and was small for gestational age, which are both known risk factors for developmental delay [23], 24]. One of the children from our cohort had severe neurodevelopmental delay and has special needs. He was born prematurely at 30 5/7 and the LOTUS study has clearly shown that prematurity is a significant risk factor for neurodevelopmental delay in HDFN [25]. The total bilirubin level at birth was high, 270 μmol/L, and he required ET. Data on acute bilirubin-induced neurological dysfunction are missing from the medical records, and brain MRI was not performed, therefore bilirubin toxicity cannot be excluded. Overall rate of adverse long-term neonatal outcomes in our study was 11.8 %, consistent with the rate reported in the literature and it is likely that the neurodevelopmental delay is due to prematurity rather than severity of HDFN [16], 25].

Conclusions

In conclusion, HDFN is not obsolete, and awareness of its potential severity in affected pregnancies is essential. Cases of severe HDFN may have excellent outcomes if the pregnancies receive multidisciplinary and timely management. Referral should be made early in the course of the disease, which is enabled by the nationwide screening programs. Structured fetal monitoring is essential and a timely decision for fetal therapy must be made to achieve the best outcomes. As most newborns will require postnatal care, they should be born in a specialized unit with a high-quality NICU.