Omission of fetal sampling in treatment of subsequent pregnancies in fetal-neonatal alloimmune thrombocytopenia

Does anti-HPA-1a affect birthweight in fetal and neonatal alloimmune thrombocytopenia?

BACKGROUND

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) ensues from parental incompatibility for platelet alloantigens with maternal sensitization. HPA-1a/1b incompatibility is the most common cause of FNAIT in Caucasians. Placental villitis and lower birthweight in FNAIT suggest anti-HPA-1a may have effects beyond inducing thrombocytopenia.

OBJECTIVES

Does FNAIT secondary to anti-HPA-1a result in smaller newborns and, the corollary, does antenatal management of FNAIT increase birthweight?

STUDY DESIGN

Birthweights of 270 FNAIT-affected newborns from a randomized clinical trial and a NAITbabies.org survey (135 paired siblings) were compared with those of published controls and treated to untreated FNAIT-affected siblings. Birthweights were converted to percentiles to account for gestational age, sex, and role of birth order in birth weight. Body weights of FNAIT-affected and -unaffected pups in a mouse FNAIT model were analyzed.

RESULTS

Untreated siblings in both the clinical trial and NAITbabies.org cohorts were not small, compared with normal controls. However, treated siblings in both cohorts had significantly higher birthweight percentiles compared with their previous untreated affected sibling. After accounting for gestational age, sex, and birth order, increased birthweight percentile in treated compared with the untreated siblings remained significant in both cohorts. FNAIT-affected neonatal mice had lower bodyweights than FNAIT-unaffected pups.

CONCLUSIONS

Untreated FNAIT-affected newborns were not small; however, treatment of FNAIT-affected pregnancies increased newborn birthweights despite corrections to account for other factors that might have influenced the results. High dose IVIG is believed to "block" FcRn and lower maternal anti-HPA-1a levels, and thus increase birthweights by reducing levels of maternal anti-HPA-1a and reducing placental villitis.

Fetal and neonatal alloimmune thrombocytopenia: A rare case report of prenatal treatment

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a rare but serious condition. The first-line antenatal management of FNAIT consists of weekly IVIG with or without corticosteroids, ideally starting before 16 weeks of gestation.

Immune-Mediated Neonatal Thrombocytopenia

Immune-mediated thrombocytopenia in neonates is caused by the transplacental passage of maternally derived antiplatelet antibodies. The 2 most common causes include neonatal alloimmune thrombocytopenia, which leads to significant thrombocytopenia and risk of intracranial hemorrhage, and autoimmune thrombocytopenia, which is generally less severe. No specific guidelines for prenatal management exist for either disease; however, intravenous immune globulin treatments and systemic steroids for women with at-risk pregnancies can be useful in both diseases. In this review, we discuss the current literature and management strategies for both pregnant women and newborns with immune-mediated thrombocytopenia.

New developments in fetal and neonatal alloimmune thrombocytopenia

Fetal and neonatal alloimmune thrombocytopenia, the platelet equivalent of hemolytic disease of the fetus and newborn, can have devastating effects on both the fetus and neonate. Current management of fetal and neonatal alloimmune thrombocytopenia in a subsequent affected pregnancy involves antenatal administration of intravenous immune globulin and prednisone to the pregnant woman to prevent the development of severe fetal thrombocytopenia and secondary intracranial hemorrhage in utero. That therapy has proven to be highly effective but is associated with maternal side effects and is expensive. This commentary describes 4 advances that could substantially change the current approach to detecting and managing fetal and neonatal alloimmune thrombocytopenia in the near future. The first would be an introduction of a program to screen all antepartum patients in this country for pregnancies at risk of developing fetal and neonatal alloimmune thrombocytopenia. Strategies to implement this complex process have been described. A second advance is testing of cell-free fetal DNA obtained from maternal blood to noninvasively determine the fetal human platelet antigen 1 genotype. A third, in preliminary development, is creation of a prophylactic product that would be the platelet equivalent of Rh immune globulin (RhoGAM). Finally, a fourth major potential advance is the development of neonatal Fc receptor inhibitors to replace the current medical therapy administered to pregnant women with an affected fetus. Neonatal Fc receptor recycles plasma immunoglobulin G to increase its half-life and is the means by which immunoglobulin G crosses the placenta from the maternal to the fetal circulation. Blocking the neonatal Fc receptor is an ideal way to prevent maternal immunoglobulin G antibody from causing fetal and neonatal alloimmune thrombocytopenia in a fetus at risk of developing that disorder. The pertinent pathophysiology and rationale for each of these developments will be presented in addition to our thoughts relating to steps that must be taken and difficulties that each approach would face for them to be successfully implemented.

Neonatal Alloimmune Thrombocytopenia: A Concise Review

BACKGROUND

Neonatal alloimmune thrombocytopenia (NAIT) is defined as an uncommon platelet disorder caused by maternal alloimmunization to human-specific antigens (HPAs) that are paternally inherited, resulting in low fetal/neonatal platelet levels and debilitating effects on the newborn. The incidence of NAIT is 1 in every 1000 live births within the United States; it is the most common cause of severe thrombocytopenia (<30 × 109/L) and intracranial hemorrhage in term newborns.

PURPOSE

The purpose of this article is to discuss the pathophysiology, clinical manifestations, diagnosis, and treatment of NAIT and its implications upon the lifespan of the neonate.

METHODS

A literature review was conducted using PubMed, CINAHL, and Google Scholar (2014-2019). Search terms included NAIT, neonatal/fetal alloimmune thrombocytopenia, newborn platelets, and intracranial bleeding and NAIT.

RESULTS

NAIT can affect first pregnancies and often goes undiagnosed until delivery. Universal screening tools with a focus on HPA-1a typing via noninvasive testing have been successfully trialed and have yielded promising results indicating a 75% reduction in risks associated with NAIT; however, none have been incorporated into practice and prophylactic treatment remains unavailable.

IMPLICATIONS FOR RESEARCH

Adopting a universal screening tool and prophylaxis for NAIT would allow for early diagnosis and treatment in utero.

IMPLICATIONS FOR PRACTICE

Many healthcare providers are not familiar with NAIT often focusing on other causes of thrombocytopenia as a potential diagnosis.

Non-invasive risk-assessment and bleeding prophylaxis with IVIG in pregnant women with a history of fetal and neonatal alloimmune thrombocytopenia: management to minimize adverse events

INTRODUCTION

In pregnant women with a history of fetal and neonatal alloimmune thrombocytopenia (FNAIT), prenatal intervention in subsequent pregnancies may be required to prevent fetal bleeding. Several invasive and non-invasive protocols have been published: amniocentesis for fetal genotyping, fetal blood sampling for the determination of fetal platelet count, intrauterine platelet transfusions, and weekly maternal i.v. immunoglobulin (IVIG) infusion with or without additional corticosteroid therapy. This is the first retrospective study that report the experience with a non-invasive protocol focused on side effects of maternal IVIG treatment and neonatal outcome.

METHODS

Pregnant women with proven FNAIT in history and an antigen positive fetus were treated with IVIG (1 g/kg/bw) every week. To identify potential IVIG-related hemolytic reactions isoagglutinin titer of each IVIG lot and maternal blood count were controlled. IVIG-related side effects were prospectively documented and evaluated. Furthermore, ultrasound examination of the fetus was performed before starting IVIG administration and continued regularly during treatment. Outcome of the index and subsequent pregnancy was compared. Corresponding data of the newborns were analyzed simultaneously.

RESULTS

IVIG was started at 20 weeks of gestation (median). Compared to the index pregnancy, platelet counts of the newborns were higher in all cases. No intracranial hemorrhage occurred (Index pregnancies: 1 case). Platelet counts were 187 × 10⁹/l (median, range 22-239, 95% CI) and one newborn had mild bleeding. No severe hemolytic reaction was observed and side effects were moderate.

CONCLUSION

Among pregnant women with FNAIT history, the use of non-invasive fetal risk determination and maternal IVIG resulted in favorite outcome of all newborns. Invasive diagnostic or therapeutic procedures in women with a history of FNAIT should be abandoned.

Fetal and neonatal alloimmune thrombocytopenia: recommendations for evidence-based practice, an international approach

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) may result in severe bleeding, particularly fetal and neonatal intracranial haemorrhage (ICH). As a result, FNAIT requires prompt identification and treatment; subsequent pregnancies need close surveillance and management. An international panel convened to develop evidence-based recommendations for diagnosis and management of FNAIT. A rigorous approach was used to search, review and develop recommendations from published data for: antenatal management, postnatal management, diagnostic testing and universal screening. To confirm FNAIT, fetal human platelet antigen (HPA) typing, using non-invasive methods if quality-assured, should be performed during pregnancy when the father is unknown, unavailable for testing or heterozygous for the implicated antigen. Women with a previous child with an ICH related to FNAIT should be offered intravenous immunoglobulin (IVIG) infusions during subsequent affected pregnancies as early as 12 weeks gestation. Ideally, HPA-selected platelets should be available at delivery for potentially affected infants and used to increase the neonatal platelet count as needed. If HPA-selected platelets are not immediately available, unselected platelets should be transfused. FNAIT studies that optimize antenatal and postnatal management, develop risk stratification algorithms to guide management and standardize laboratory testing to identify high risk pregnancies are needed.

Management and Neonatal Outcomes of Pregnancies with Fetal/Neonatal Alloimmune Thrombocytopenia: A Single-Center Retrospective Cohort Study

BACKGROUND

There is no consensus regarding the optimal antenatal treatment of fetal/neonatal alloimmune thrombocytopenia (F/NAIT). We aimed to review the fetal blood sampling (FBS)-related risk, fetal response to maternal intravenous immunoglobulin (IVIG), and cesarean section (CS) rate in pregnancies with a history of F/NAIT.

METHODS

Maternal demographics, alloantibodies, pregnancy management, fetal and neonatal outcomes, and index case characteristics were collected. Responders (R) and non-responders (NR) were defined as women treated with IVIG in whom fetal platelets (PLTs) were normal or low (< 50 × 109/L).

RESULTS

An FBS-related risk occurred in 1.6% (2/119) of procedures. Maternal characteristics did not differ between responders (n = 21) and non-responders (n = 21). HPA-1a antibody was detected in all non-responders and in 72% of responders (p < 0.01). The index case had a significantly lower PLT count at birth in non-responders versus responders (median PLT count: R = 20 × 109/L [IQR 8-43] vs. NR = 9 × 109/L [IQR 4-18], p < 0.02). No differences were found in IVIG treatment duration or dosage. PLTs at birth were significantly lower in non-responders compared to responders. No intracranial hemorrhages occurred. CSs were performed for obstetric indications only in all but two cases.

CONCLUSION

Maternal IVIG can elicit different fetal responses. The lack of prognostic factors to predict responders or non-responders suggests that there remains a role for FBS in F/NAIT in experienced hands.

Imaging and management of fetuses and neonates with alloimmune thrombocytopenia

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is the most common cause of severe neonatal thrombocytopenia and intracranial bleeding in term newborns. Intracranial hemorrhage (ICH) commonly results in death or severe, lasting neurologic disability. The timing of ICH is also important for management of the next affected pregnancy in cases of FNAIT. This manuscript reviews the advantages and disadvantages of the different radiologic methodologies to identify and characterize ICH. It discusses the limits of ultrasound and the advantages of magnetic resonance imaging allowing avoidance of the radiation associated with computed tomography (CT) scans.

Current perspectives on fetal and neonatal alloimmune thrombocytopenia - increasing clinical concerns and new treatment opportunities

Differences in platelet type between the fetus and the mother can lead to maternal immunization and destruction of the fetal platelets, a condition named fetal and neonatal alloimmune thrombocytopenia (FNAIT). FNAIT is reported to occur in ~1 per 1,000 live born neonates. The major risk is intracranial hemorrhage in the fetus or newborn, which is associated with severe neurological complications or death. Since no countries have yet implemented a screening program to detect pregnancies at risk, the diagnosis is typically established after the birth of a child with symptoms. Reports on broader clinical impact have increased clinical concern and awareness. Along with new treatment options for FNAIT, the debate around antenatal screening to detect pregnancies at risk of FNAIT has been revitalized.