• Heparin treatment;
  • immunoglobulin G;
  • implantation;
  • inflammation;
  • obstetrical complications;
  • trophoblast


  1. Top of page
  2. Abstract
  3. Introduction
  4. Antiphospholipid antibody manifestation in women with RPL
  5. Immunopathology of APS
  6. Placental pathology and micro-angiopathy induced by aPL
  7. Role of aspirin and heparin in aPL-mediated immunopathology
  8. Anticoagulation treatment in women with aPL and RPL
  9. Should treatment be different based on aPL titer, isotype, single, or multiple epitopes?
  10. Non-anticoagulant treatment for women with aPL and RPL
  11. Conclusion
  12. References

Antiphospholipid antibodies (aPL) have been associated with recurrent pregnancy losses (RPL) and other obstetrical complications. The diagnostic criteria for the classical antiphospholipid antibody syndrome (APS) have been utilized for the detection of obstetrical APS in women with RPL. However, laboratory findings and immunopathology of obstetrical APS are significantly different from those of classical APS. In addition, many women with RPL who have positive aPL do not have symptoms consistent with the current APS criteria. The induction of a proinflammatory immune response from trophoblasts and complement activation by aPL rather than thromboembolic changes has been reported as a major immunopathological feature of obstetrical APS. Heparin treatment has been reported to be effective in prevention of early pregnancy loss with APS but not for the late pregnancy loss or complications. The complex effects of heparin may explain the limited efficacy of heparin treatment in RPL. New diagnostic criteria for obstetrical APS are needed urgently, and new therapeutic approaches should be explored further.


  1. Top of page
  2. Abstract
  3. Introduction
  4. Antiphospholipid antibody manifestation in women with RPL
  5. Immunopathology of APS
  6. Placental pathology and micro-angiopathy induced by aPL
  7. Role of aspirin and heparin in aPL-mediated immunopathology
  8. Anticoagulation treatment in women with aPL and RPL
  9. Should treatment be different based on aPL titer, isotype, single, or multiple epitopes?
  10. Non-anticoagulant treatment for women with aPL and RPL
  11. Conclusion
  12. References

The antiphospholipid antibody syndrome (APS) is a systemic autoimmune disorder that is characterized by the presence of serum antiphospholipid antibodies (aPL) and associated clinical manifestations, such as arterial thrombosis, venous thrombosis and/or obstetrical complications, especially recurrent pregnancy losses (RPL).[1, 2] Approximately, 20% of women with RPL have autoimmune abnormalities[3] and aPL is one of the most common autoimmune etiologic factor for RPL.[1, 4, 5] Fifteen percentage of women with three or more RPL were reported to have persistently positive aPL,[6] and the fetal loss rate of these women was reported to be 50–90% if no specific treatment was given.[7, 8]

APS is defined as IgG and/or IgM anti-cardiolipin antibody (aCL) at a medium or high titer level (over the 99th percentile of a normal population), anti-β2 glycoprotein-I (β2GPI) antibody (over the 99th percentile), and lupus anticoagulant (LA) by the revised Sapporo criteria in 2006.[2] In addition to laboratory assays, clinical criteria are utilized for the diagnosis of APS. Recently, the revised APS criteria have reflected the association of APS with more obstetrical complications; however, controversies and uncertainty regarding diagnosis and treatment still persist.[2, 9]

Our understanding regarding the possible etiology and pathogenesis of this syndrome is limited. APS has been generally considered as a thrombophilic disease. Hence, the treatment has been primarily focused on anticoagulation using heparin and aspirin. However, recent findings from APS research using animal models have demonstrated that APS-induced obstetrical complications are initiated by inflammation rather than thrombosis.[10-12] These studies suggest that anti-inflammatory treatment should be considered for APS management. This review will discuss the characteristics of aPL expression in women with RPL, the potential mechanisms of tissue injury by aPL, how heparin therapy might inhibit the pathogenic mediators of disease, and the management of obstetrical APS.

Antiphospholipid antibody manifestation in women with RPL

  1. Top of page
  2. Abstract
  3. Introduction
  4. Antiphospholipid antibody manifestation in women with RPL
  5. Immunopathology of APS
  6. Placental pathology and micro-angiopathy induced by aPL
  7. Role of aspirin and heparin in aPL-mediated immunopathology
  8. Anticoagulation treatment in women with aPL and RPL
  9. Should treatment be different based on aPL titer, isotype, single, or multiple epitopes?
  10. Non-anticoagulant treatment for women with aPL and RPL
  11. Conclusion
  12. References

There are significant differences in the presence of the types of aPL in women with RPL and classical APS patients (Table 1). aPL are a heterogeneous group of autoantibodies, and their presence is associated with thrombosis and RPL.[1, 13] Regardless of the levels of positive aCL, antibodies directed against phospholipid-binding plasma proteins such as β2GPI, prothrombin (PT), and annexin V have also been reported to constitute a risk factor for thromboembolism in patients with systemic lupus erythematosus (SLE) and for miscarriage in women with RPL.[14] Patients with primary APS (pAPS) or SLE have significantly higher prevalence of these antibodies when compared to women with RPL. IgG and/or IgM aPL, anti-β2GPI, anti-PT, and IgG anti-annexin V antibodies were detected in 100, 80, 60, and 24% of the pAPS patients, respectively. In contrast, 66% of women with RPL were negative for all antibodies, and the prevalence of IgG and/or IgM aCL, anionic phospholipid antibody, anti-β2GPI, anti-PT, and IgG anti-annexin V antibodies was 6, 12, 6, 16, and 17%, respectively.[14] The titer and concentration of these antibodies were significantly higher in patients with pAPS and SLE as compared to women with RPL.[14] Thrombosis (54–67%) and thrombocytopenia (24–36%) are frequently present in women with SLE and APS; however, those are rarely found in women with RPL.[14-16]

Table 1. Comparison of Clinical and Laboratory Manifestations of Women with Systemic Lupus Erythematosus (SLE) or Recurrent Pregnancy Loss (RPL) among Antiphospholipid Antibody Syndrome (APS) Patients
  1. aPL, antiphospholipid antibodies.

  2. a


  3. b


  4. c


aPL prevalenceHighaLowb
IgG CL53%13%
IgG PA37%9%
IgG PI32%11%
IgG PS38%15%
aPL titerModerate to highLow to moderate
aPL concentration×3–10 higher than RPLLow
Thrombosis54–67% of aPL+ patientcPresent in placenta
Thrombocytopenia24–36% of aPL+ patientc

Women with RPL have a significantly higher prevalence of aPL directed against anionic phospholipids such as anti-phosphatidylserine or anti-phosphatidylethanolamine antibody as compared to normal controls,[16, 17] and pregnant women with RPL tend to have increased aPL prevalence as compared to normal pregnant women.[18] When we analyzed 320 women with RPL who visited Reproductive Medicine Clinic at Rosalind Franklin University of Medicine and Science, the majority of RPL women with positive aCL or anionic phospholipid antibodies had borderline to moderate positive titer antibodies and fewer patients had high titer aPL (Fig. 1). Although the presence of these other antibodies is not considered an indication of the classical APS, when these patients were treated with heparin and aspirin, 64% of women with antibodies to anionic phospholipids responded to the treatment and delivered a live-born infant.[17] Therefore, the current definition of aPL, which is limited to only aCL, LA and anti-β2GPI antibody, may not be broad enough to include women with RPL- and aPL-related pathology and should be re-evaluated.


Figure 1. Prevalence and titer distribution of antiphospholipid antibodies (aPL) in women with three or more recurrent pregnancy losses (n = 320). Green bar designates for high titer aPL, red for positive and blue for borderline titer. (IgG, immunoglobulin G; CL, cardiolipin; PE, phosphatidylethanolamine; PI, phosphatidyl inositol; PA, phosphatidic acid; PG, phosphatidyl glycerol; PS, phosphatidyl serine).

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Obstetrical APS is defined as appearing in women with obstetrical complications such as early RPL, fetal death, delivery <34 weeks due to severe pre-eclampsia or placental insufficiency, post-partum and long-term complications, and laboratory tests indicating the presence of APS.[19] In particular, the HELLP (hemolysis, elevated liver enzymes, low platelet count) syndrome was suggested to be included in microvascular and microangiopathic antiphospholipid-associated syndrome (MAPS).[20] Microvascular thrombotic and underestimated microangiopathic histopathological lesions in placenta of women with RPL and aPL have not been investigated well and need more study in the future.

Immunopathology of APS

  1. Top of page
  2. Abstract
  3. Introduction
  4. Antiphospholipid antibody manifestation in women with RPL
  5. Immunopathology of APS
  6. Placental pathology and micro-angiopathy induced by aPL
  7. Role of aspirin and heparin in aPL-mediated immunopathology
  8. Anticoagulation treatment in women with aPL and RPL
  9. Should treatment be different based on aPL titer, isotype, single, or multiple epitopes?
  10. Non-anticoagulant treatment for women with aPL and RPL
  11. Conclusion
  12. References

Several mechanisms have been proposed to explain the clinical manifestations associated with aPL. First, aPL have been shown to cause activation in cells such as platelets, endothelial cells, and monocytes.[21-23] In the context of the thrombotic tendency of the disease and the observation that thrombocytopenia is a frequent manifestation in APS,[15] we can surmise that platelet activation may be an integral part of aPL-induced immunopathology. aPL have been shown to increase the expression of glycoproteins on the membrane of the platelet, particularly GPIIb/IIIa (a fibrinogen receptor important in platelet aggregation) and GPIIIa.[13] There is also convincing evidence that aPL can activate endothelial cells and monocytes in vivo and in vitro, and this activation can be demonstrated by the increased expression of different cellular adhesion molecules and tissue factor (TF).[24-30] The thrombotic tendency induced by aCL was reported to be related to the titer, but not the titers of anionic phospholipid antibodies.[15] This finding was also supported by an animal study which revealed a dose-dependent effect of white blood cell sticking to endothelial cells induced by aCL present in the sera of the mice.[31]

Second, aPL induces thrombosis in the placenta and the vascular bed by interfering with the annexin A5 anticoagulant shield on phospholipid expressing surfaces.[32, 33] Clustering of annexin A5 on phospholipid surface results in displacement of clotting factor Va, precluding formation of procoagulant complexes. In murine studies, it has been demonstrated that passive transfer of a human monoclonal aPL, CIC15, isolated from a patient with pAPS and RPL, induced fetal resorption.[34] Histological analysis revealed signs of decidual arterial thrombosis, but there was no evidence of inflammatory cell infiltration in the decidual or fetal tissue. Pregnancy loss in this setting was reported to be related to the procoagulant activity of CIC15 but not due to disrupting annexin A5, because CIC15 was not able to disrupt the two-dimensional ordered arrays of annexin A5.[34] Therefore, the induction of thrombosis by aPL in the placenta and the vascular bed may involve various pathways.

Third, aPL have been shown to alter the maturation, movement, and invasiveness of trophoblast cells. Histopathological examination of products of conception in women with pAPS and pregnancy losses between 7 and 10 weeks gestation attributed these losses to abnormal endovascular trophoblast invasion in decidual vessels rather than excessive villous thrombosis.[35] This finding suggests that aPL cause defective placentation,[36] and that thrombophilia is not the sole explanation for complications of pregnancy in patients with APS. Indeed, anti-β2GPI antibodies have been reported to trigger an inflammatory response in trophoblast cells by increasing secretion of IL-8, MCP-1, GRO-α, and IL-1β. At high concentrations, these antibodies also induce caspase-mediated cell death.[37] Therefore, by acting in an autocrine and paracrine manner, anti-β2GPI antibodies induce inflammatory mediators to compromise trophoblast survival. In addition, aPL limit trophoblast cell migration by down-regulating trophoblast IL-6 secretion and STAT3 activity.[38] Hence, women with aPL and RPL have increased risk of developing obstetrical complications, associated with impaired deep placentation, such as pre-eclampsia.[38] aPL significantly reduce both VEGF and MMPs production, and at the nuclear level, NFκB DNA binding activity.[36] aPL recognize anionic phospholipids and β2GPI, which have adhered onto trophoblast cell structures, and significantly reduce β–hCG release and Matrigel invasiveness.[39] Therefore, aPL can impair trophoblast cell maturation, mobility, and invasiveness as well.

Activation of the complement cascade has attracted much attention in recent years in the context of obstetrical APS. Inflammation is now believed to be at the core of the pathogenesis of this syndrome, and tissue injury is speculated to be the result of complement-mediated inflammatory reaction in addition to thrombosis. Findings from animal models of aPL-induced pregnancy loss and increased injury-induced thrombosis argue that complement factor C3 and C5 are essential proximal mediators of tissue injury.[10, 39, 40] The complement system is capable of producing the thrombotic manifestations of APS through the direct activation of the coagulation cascade via membrane attack complex or indirectly via C5a-C5a receptor interaction leading to upregulation of TF, and thus activating the coagulation cascade.[11] In addition, complement activation leads to recruitment and stimulation of inflammatory cells and injury to the developing fetal-placental unit.

Placental pathology and micro-angiopathy induced by aPL

  1. Top of page
  2. Abstract
  3. Introduction
  4. Antiphospholipid antibody manifestation in women with RPL
  5. Immunopathology of APS
  6. Placental pathology and micro-angiopathy induced by aPL
  7. Role of aspirin and heparin in aPL-mediated immunopathology
  8. Anticoagulation treatment in women with aPL and RPL
  9. Should treatment be different based on aPL titer, isotype, single, or multiple epitopes?
  10. Non-anticoagulant treatment for women with aPL and RPL
  11. Conclusion
  12. References

When placenta from women with RPL are reviewed for histological properties, inadequate cytotrophoblast invasion depth (54%), disrupted syncytium formation (44%), thromboembolism in decidual vessels (33.9%), and elevated CD57+ NK cells infiltration (29.6%) are often present.[41] In women with aPL without any history of RPL, 36% of non-treated women who miscarry prior to 18 weeks gestation demonstrated chronic intervillositis and none had typical aPL-related pathology.[42] Sebire et al.,[35] reported that defective decidual endovascular trophoblast invasion, rather than excessive intervillous thrombosis, is the most frequent histological abnormality in aPL-associated early pregnancy loss as compared to aPL-negative pregnancy loss and normal controls. Therefore, thrombotic placental pathology is not specific for aPL-related pregnancy losses.

Lack of thrombotic changes at maternal fetal junction has been also demonstrated in an animal model treated with aPL. Mice that received IgG containing aPL showed strong TF staining throughout the decidua and on embryonic debris. TF staining was not associated with either fibrin staining or thrombi in decidua. The absence of fibrin deposition and thrombi suggests that TF-dependent activation of coagulation does not directly mediate aPL-induced pregnancy loss.[43] Inflammation, especially complement activation with generation of the anaphylotoxin C5a, has been reported to be an essential mediator of aPL-induced fetal injury. aPL induces TF expression, which leads to cell signaling activity.[43, 44] Recently, in a study of women with SLE and APS, it has been reported that classical complement activation plays a major role in aPL-mediated fetal injury and that placental C4d deposition is a reflection of classical complement activation in women with APS.[12]

Similar pathological findings have been reported in endometrium of women with aPL. Although aPL have been reported to activate endothelial cells in vivo, and create a prothrombotic state on endothelial cells,[31] thrombotic occlusion or intimal thickening affecting endometrial blood vessels is not often detected by hematoxylin–eosin staining of specimens from women with aPL. Instead, endometrial and subendometrial vascularity measured by Doppler ultrasound was significantly impaired in women with RPL and aPL during midluteal phase compared with normal fertile women.[45] Impaired endometrial vascularity may be the common effect induced by heterogeneous etiologic factors in women with RPL and aPL and unexplained RPL. Inflammation induced by aPL may lead to defective decidual endovascular trophoblast invasion during early implantation.

Role of aspirin and heparin in aPL-mediated immunopathology

  1. Top of page
  2. Abstract
  3. Introduction
  4. Antiphospholipid antibody manifestation in women with RPL
  5. Immunopathology of APS
  6. Placental pathology and micro-angiopathy induced by aPL
  7. Role of aspirin and heparin in aPL-mediated immunopathology
  8. Anticoagulation treatment in women with aPL and RPL
  9. Should treatment be different based on aPL titer, isotype, single, or multiple epitopes?
  10. Non-anticoagulant treatment for women with aPL and RPL
  11. Conclusion
  12. References

Recently, the use of combined unfractionated heparin (UFH) and low-dose aspirin regimen was reported to reduce the risk of spontaneous pregnancy loss by 54%, resulting in a live birth rate of 70–80%.[46, 47] However, histological studies of the APS patients or animal models often demonstrated the absence of thrombosis from miscarriage samples.[11, 35] Thus, it was postulated that inflammation may be the culprit in the aPL-induced pregnancy loss.

Aspirin is commonly prescribed to women at high risk of obstetric complications. The antithrombotic properties of aspirin may act to improve blood flow in the uterine vessels via inhibition of thromboxane A2, which is required for platelet aggregation.[48] Aspirin can also stimulate IL-3, an essential factor for implantation and placental growth; hence, more favorable embryonic implantation may be induced.[49] Aspirin and heparin combined therapy was reported to have a better success rate than aspirin monotherapy alone.[50] In a pilot double blinded randomized controlled trial, it was found that there was no significant difference in the aspirin and placebo treatment groups, reporting a live birth rate of 80 and 85%, respectively.[51] Therefore, the therapeutic effect of aspirin monotherapy for women with RPL and aPL seems to be limited.

Heparin has various pharmacological actions including direct interaction with trophoblasts (Table 2), and heparin treatment can result in a significant reduction in pregnancy complications in women with aPL. aPL has been shown to have a direct effect on trophoblasts unrelated to thrombosis and may induce direct cellular injury, apoptosis, inhibition of proliferation and syncytia formation, decreased human chorionic gonadotropin production, and defective invasiveness.[35, 36, 52, 53] All of these aPL-mediated effects might play a role in defective placentation. Heparin was reported to suppress some of these aPL-related pathology but not all.[37, 38] Therefore, heparin seems to have limited efficacy for aPL-related immunopathology during pregnancy.

Table 2. Action of Heparin on Immune Response
  1. aPL, antiphospholipid antibodies; LMWH, low molecular weight heparin.

1. Suppression of natural killer cell cytotoxicity[107]
2. Prevention of aPL-induced trophoblast inflammation and inhibition of aPL-triggered trophoblast cell death[57]
3. Prevention of leukocyte adhesion[108]
4. Blockage of interferon-γ signaling[109]
5. Inhibition of complement activation and promotion of growth factors[57]
6. Abrogates apoptosis of primary first trimester villous trophoblast in response to treatment with the pro-inflammatory cytokines, interferon (IFN)-gamma, and tumor necrosis factor (TNF)-alpha[58]
7. Attenuated the anti-β2-GPI antibody-mediated cell death, and the pro-inflammatory response, but only at high concentrations[37]
8. Unable to reverse the effects of anti-β2-GPI mAbs on trophoblast IL-6 production and migration by both unfractionated heparin and LMWH[38]
9. Upregulates soluble fms-like tyrosine kinase receptor-1 (sFlt-1) secretion independently of aPL by LMWH[67]

Heparin prevents the binding of β2GPI to negatively charged phospholipid which in turn prevents the deposition of anti-β2GPI antibodies in tissues.[54] Indeed, low molecular weight heparin (LMWH) has been shown to be able to reduce the binding of aPL to trophoblast cells and restore in vitro placental invasiveness and differentiation.[55, 56] Excessive activation of complement system at feto-maternal interface has been proposed as additional aPL-mediated mechanism of placental damage. Treatment with heparin prevented complement activation in vivo and protected mice from pregnancy complications induced by aPL.[57]

Heparin is also a modulator of inflammatory responses. Heparin abrogates apoptosis of primary first trimester villous trophoblast in response to treatment with the proinflammatory cytokines such as IFN-γ and TNF-α and sera from women with IVF failures and APS, and inhibited apoptosis induced by other agents including staurosporin, a broad-spectrum kinase inhibitor, and thrombin.[58, 59] It has been also reported that such low doses of heparin, lacking anticoagulant effects, inhibited an inflammatory response at the level of leukocyte adhesion and influx, and limited tissue injury.[60-62] Heparin possesses the ability to inhibit lipopolysaccharide-induced proinflammatory cytokines, such as TNF-α, IL-6, IL-8, and IL-1β involved in RPL of a murine model of APS.[63] For these anti-inflammatory actions, heparin has been suggested as a useful management tool for at risk patients, even in the absence of an identifiable thrombophilic disorder.[58]

Heparin has been reported to promote angiogenesis and support endovascular cross talk between the trophoblast and endothelial cells.[64] Interestingly, in the absence of aPL, LMWH induces potentially detrimental proinflammatory and anti-angiogenic profile in the trophoblast. In the presence of aPL, LMWH counters trophoblast inflammation, but induces an anti-angiogenic response.[65] LMWH enhanced placental growth factor (PlGF) secretion from trophoblast. However, LMWH up-regulated soluble fms-like tyrosine kinase receptor-1 (sFlt-1) secretion independently of aPL through shedding of the extracellular domain of Flt-1 receptor.[66] The complicated effects of heparin may explain why women with RPL, who were treated with heparin to prevent early pregnancy loss, have inconsistent outcome and still remain at increased risk of developing later obstetrical complications such as pre-eclampsia.[67]

In a recent clinical trial, heparin treatment was reported to be associated with increased circulating levels of sFlt-1 in the third trimester without increased growth restriction, and serum of heparin-treated cases inhibited both basal and vascular endothelial growth factor-induced capillary-like tube formation.[66] Therefore, upregulation of circulating sFlt-1 immunoreactivity in pregnancy seems not always to be associated with adverse outcomes and whether heparin has any effect to promote angiogenesis is in question.[66]

Anticoagulation treatment in women with aPL and RPL

  1. Top of page
  2. Abstract
  3. Introduction
  4. Antiphospholipid antibody manifestation in women with RPL
  5. Immunopathology of APS
  6. Placental pathology and micro-angiopathy induced by aPL
  7. Role of aspirin and heparin in aPL-mediated immunopathology
  8. Anticoagulation treatment in women with aPL and RPL
  9. Should treatment be different based on aPL titer, isotype, single, or multiple epitopes?
  10. Non-anticoagulant treatment for women with aPL and RPL
  11. Conclusion
  12. References

Numerous trials have been performed to assess the efficacy of prophylactic anticoagulation in women with RPL and aPL, and UFH has been the anticoagulant of choice during pregnancy.[68] However, reports of treatment outcome have been inconsistent, perhaps due to the heterogeneity of patient population.[46] For example, number of pregnancy losses; inclusion of chemical pregnancy; 1st versus 2nd trimester losses; primary versus secondary abortion; APS versus non-classical aPL; laboratory criteria (such as aCL alone, LA alone, both aCL and LA, or non-classical aPL); isotype and titers of aPL, etc. are different from one study to another and makes it difficult to compare these studies. Treatment has also been started at various time frames, such as pre-conception, post-conception, or with positive fetal heart beat.[46] Recent studies have assessed the efficacy of LMWH due to the advantage of easier administration and lower incidence of osteoporosis and heparin-induced thrombocytopenia compared to UFH.[69-71]

Evidence from small controlled trials have suggested that patients with RPL associated with aPL and without prior thromboembolism benefit from treatment with low-dose UFH at prophylactic doses of 5000–10,000 IU twice daily in addition to low-dose aspirin at 70–81 mg daily.[50, 72] Based on previous trials, Cochrane review concluded that the addition of UFH to aspirin may reduce pregnancy loss by 54% (RR 0.46), but LMWH and aspirin treatment did not significantly reduce pregnancy loss although the point estimates were in the direction of benefit suggesting LMWH probably has some benefit.[46] In a recent meta-analysis by Ziakas, heparin treatment (overall for UFH and LMWH treatment) was reported to be effective in early pregnancy loss in aPL patients (P < 0.0001), but not in late pregnancy loss (P = 0.9).[73] When LMWH and aspirin treatment was directly compared with UFH and aspirin treatment, there were no differences in pregnancy outcome.[74, 75] It has also been reported that no patients had spinal or epidural anesthesia and there was no complications overall.[75] LMWH and UFH have similar effects on aPL binding in vitro. No excessive bleeding in women with either vaginal or cesarean deliveries, no evidence of heparin-induced thrombocytopenia, or osteoporosis were reported.[76, 77] Therefore, both UFH with aspirin and LMWH with aspirin treatment can be utilized for women with aPL and RPL.

Should treatment be different based on aPL titer, isotype, single, or multiple epitopes?

  1. Top of page
  2. Abstract
  3. Introduction
  4. Antiphospholipid antibody manifestation in women with RPL
  5. Immunopathology of APS
  6. Placental pathology and micro-angiopathy induced by aPL
  7. Role of aspirin and heparin in aPL-mediated immunopathology
  8. Anticoagulation treatment in women with aPL and RPL
  9. Should treatment be different based on aPL titer, isotype, single, or multiple epitopes?
  10. Non-anticoagulant treatment for women with aPL and RPL
  11. Conclusion
  12. References

The Titers of aPL and Treatment Outcome

Current treatment of APS is mainly based on the clinical presentation and laboratory tests. Some studies showed that the high positive aPL titers were associated with adverse pregnancy outcome. In a retrospective cohort study by Simchen et al.,[78] women with APS were divided into two groups: high positive titer group with antibody titers greater than four times the upper limit of normal, and the rest as positive titer group. All women were treated with daily enoxaparin (LMWH) and aspirin. The results indicated that the risk for adverse fetal/neonatal outcome was 5.7 times higher (95%CI 1.9–17.7) in women with high positive aPL titers than in those with positive titers. It is suggested that pregnant women with APS and high positive aPL titers are a unique and extremely high-risk group for adverse fetal/neonatal outcome. Strict surveillance and possible additional therapy options should be explored for this patient population.

Although high titer aPL was reported to be related to thrombotic events, several studies reported that patients with thrombotic complications have low antibody levels.[79, 80] In case of early RPL and fetal death, the intermediate or low aPL levels commonly occur. Although these patients do not meet the revised Sapporo criteria, they are increasingly considered as having APS. Interestingly, in patients with obstetrical complications, rapid intervention with conventional treatments can much improve pregnancy outcomes. In recent years, it has been reported that ~75% of treated women with RPL and aPL have a successful delivery compared with <50% without treatment.[81]

Concerning the relationship between the low titer of aPL and treatment outcome, there are fewer reported studies. Recently, Mekinian et al.[82] analyzed the impact of low-dose aspirin (100 mg/day) with or without LMWH (40 mg enoxaparin once daily) in patients with low aPL titers (between the 90th and 99th percentile for either antibody). They compared the pregnancy and neonatal outcomes of the patients with aPL based on the Sapporo criteria with other patients with aPL-like obstetrical complications and with an aPL titer below the intermediate titers. The results showed that the patients with low aPL titers have similar outcomes in respect to obstetrical complications (RPL < 10th week of gestation, fetal death, and pre-eclampsia) as patients who meet Sapporo criteria for APS diagnosis. Therefore, conventional treatment can improve reproductive outcomes in patients with low aPL levels.

The Isotypes of aPL and Treatment Outcome

Antiphospholipid antibodies are closely associated with pregnancy complications; however, many women with aPL may have normal pregnancies. Which aPL profiles, if any, can predict pregnancy outcome in women with APS is still controversial. In a retrospective multi-center case-control analysis of 114 women with APS, simultaneous positive incidence of LA, aCL, and anti-β2GPI was the independent risk factors for pregnancy failure.[83] However, other researchers argued that presence of either anti-β2GPI or LA alone was considered as the best predictor.[84, 85]

Recently, a multicenter prospective observational study of risk factors for adverse pregnancy outcome in patients with aPL (LA, aCL, and/or anti-β2GPI) and/or SLE were undertaken by Lockshin et al.[85] The patients were treated with either LMWH or UFH. The treating physicians were blinded with regard to laboratory results. The findings showed that the aPL-positive patients with or without SLE, who had a LA at screening were at highest risk for adverse pregnancy outcome. However, LA-negative women, regardless of IgG or IgM aCL or anti-β2GPI status, were not at high risk. They suggested that LA is the only component of triple aPL positivity that has predictive power.

In contrast to the above mentioned study, the results from Umehara et al.[86] demonstrated that the aPL profile did not affect the pregnancy maintenance success rate when anticoagulant therapy was actively introduced. In this retrospective cohort study, 82 RPL patients with one or more positive aPL were under two regimens of anticoagulant therapy (a daily dose of 100 mg of aspirin alone from pre-conception until the 32nd week of pregnancy, or aspirin plus subcutaneous self-injection of 5000 units of UFH twice a day, starting from the time when the presence of the gestational sac was confirmed in the uterus until the 37th week of pregnancy). The results showed that the rates of pregnancy maintenance in the IgG group (92.7%) and the IgM group (90.0%) were not different. Regarding the number of positive aPL, the rate of pregnancy maintenance in 34 cases with single aPL was 91.2% and that in 47 cases with multiple aPL was 91.5%, also showing no significant difference. These observations have led to the conclusions that active anticoagulant therapy for aPL-positive RPL patients will result in good pregnancy outcome regardless of the isotype and the number of positive aPL.

Interestingly, there are a group to women with RPL who have IgM only aPL. We followed one case of RPL with high level of aPL, primarily of IgM isotype. IgM autoantibodies were specific to cardiolipin, phosphatidylglycerol, phosphatidylserine, and phosphatidylinositol. No IgM Abs to phosphatidylethanolamine were detected. Serum immunoglobulin levels (IgM, IgG, and IgA) were all within normal range. The monitoring of the patient's serological characteristics over a period of 2 years did not reveal the development of IgG aPL, however showed persistently high levels of the initially discovered IgM Abs. Tests for rheumatoid factor, anti-β2GPI Abs, or the screening for ANA were negative. Further serological investigation revealed a presence of anti-SSA and diagnosis of Sjogren's syndrome was made and patient was referred to a rheumatologist. An analysis of routine laboratory testing for aPL during a 5-month period (total 1067 samples) at the Clinical Immunology Laboratory, the Chicago Medical School at Rosalind Franklin University of Medicine and Science, revealed at least five patients had unique IgM only pattern in previous testing repeated in 6 weeks interval. Therefore, the prevalence of the IgM isotype of aPL only might be common in women who suffer from unexplained RPL. Therefore, these antibodies may identify additional patients with clinical features of autoimmune disease.

The Epitopes of aPL and Treatment Outcome

Currently, laboratory assays for LA, aCL, and anti-β2GPI remain the cornerstones of diagnosis. Although numerous studies have confirmed that these assays have been associated with the clinical manifestations of the syndrome, none of the assays has been uniformly specific for patients with APS. As a consequence, several new tests have been currently explored as potential alternatives to improve the sensitivity and specificity of diagnostic laboratory testing for aPL.[87]

Recent studies have investigated the clinical significance of autoantibodies specific for an epitope glycine40-arginine43 (G40-R43) in domain I of β2GPI in APS. A study from de Laat et al.[88] found that patients with antibodies against epitope G40-R43 had an 18.9-fold increased risk of thrombosis compared with patients with antibodies to other specificities. Another multicenter study from the same group reported that 55% of patients with various autoimmune diseases, all positive for anti-β2GPI, had anti-domain I antibodies.[89] These patients had an odds ratio of 3.5 for thrombosis compared to those without anti-domain 1 antibodies. Additionally, they found that anti-domain I antibodies were associated with pregnancy morbidity. Recently, Banzato et al.[90] reported that high-risk patients with APS and triple positivity (LA, IgG aCL, and IgG anti-β2GPI) had significantly higher titer of anti-domain I antibodies. Ongoing investigations are proposed focusing on answering the question whether the domain I antibodies are the only antibodies of importance for the detection of APS.[91] Moreover, awareness of an association between antibodies directed against distinct β2GPI-epitopes and specific clinical manifestations of APS can contribute to better understanding of disease patterns and complications and eventually lead to more specific ‘tailor made’ peptide therapy.[92]

Non-anticoagulant treatment for women with aPL and RPL

  1. Top of page
  2. Abstract
  3. Introduction
  4. Antiphospholipid antibody manifestation in women with RPL
  5. Immunopathology of APS
  6. Placental pathology and micro-angiopathy induced by aPL
  7. Role of aspirin and heparin in aPL-mediated immunopathology
  8. Anticoagulation treatment in women with aPL and RPL
  9. Should treatment be different based on aPL titer, isotype, single, or multiple epitopes?
  10. Non-anticoagulant treatment for women with aPL and RPL
  11. Conclusion
  12. References

Glucocorticoid and intravenous immunoglobulin G (IVIg) infusion treatment have been reported to be successful in women with aPL and RPL, although contradictory studies have been reported.[7, 93-97] Recent meta-analysis reported a significant increase in live births following IVIg use in women with secondary recurrent miscarriage although overall live birth rate was not improved.[98] We have reported that IVIg treatment significantly improved reproductive outcome in women with aPL who were refractory to anticoagulation treatment or elevated NK cell levels.[99, 100] In addition, IVIg treatment has been reported to be effective in RPL women with aPL with catastrophic APS.[101] Compared to glucocorticoid treatment, IVIg treatment resulted in significantly reduced second and third trimester obstetrical complications such as pre-eclampsia or pre-term delivery. Fewer cases of intrauterine growth restriction and neonatal intensive care admission were also reported when IVIg was added to heparin and aspirin treatment compared to heparin and aspirin treatment alone.[102] Comprehensive treatment using LDA, LMWH, corticosteroid, and IVIg was reported to improve reproductive outcome and reduced obstetric complications and to be a more effective treatment for APS than prednisone and aspirin treatment.[103] Further study is warranted in IVIg treatment for women with aPL and RPL.

Statins have been reported to inhibit endothelial activation mediated by anti-β2 GPI antibody. The inhibition of E-selectin expression exerted by fluvastatin was related to the impairment of NF-κB binding to DNA and attenuated expression of IL-6 mRNA in HUVEC exposed to anti-β2GPI antibodies to cytokines.[104] In addition, fluvastatin treatment in animal model with IgG from APS patients significantly reduced size of thrombi and number of adherent leukocytes.[105] Contradictory to this finding, pravastatin was reported not to prevent aPL-related changes in human first trimester trophoblast function.[106] Therefore, it seems to be premature to apply statin treatment in women with aPL and RPL.


  1. Top of page
  2. Abstract
  3. Introduction
  4. Antiphospholipid antibody manifestation in women with RPL
  5. Immunopathology of APS
  6. Placental pathology and micro-angiopathy induced by aPL
  7. Role of aspirin and heparin in aPL-mediated immunopathology
  8. Anticoagulation treatment in women with aPL and RPL
  9. Should treatment be different based on aPL titer, isotype, single, or multiple epitopes?
  10. Non-anticoagulant treatment for women with aPL and RPL
  11. Conclusion
  12. References

Heterogeneity of population of women with RPL and aPL is the major concern in evaluation and treatment of obstetrical APS. Current diagnostic criteria for classical APS are insufficient for women with RPL and aPL. Clearly, aPL-induced RPL is not solely due to thrombotic episodes but rather inflammatory consequences either directly on trophoblast, or endometrial/decidual vasculature. Impaired endometrial/decidual vasculature and defective placental implantation are common pathology found in those women. Further studies to control the inflammatory immune response in women with RPL and aPL, using IVIg or glucocorticoids, are needed to further improve pregnancy outcome and possibly enhance even second and third trimester obstetrical complications. In addition, new diagnostic guidelines for obstetrical APS should be established. Finally, the controversies and differing results of current anticoagulation treatment highlight the urgent need for large prospective controlled trials to identify the specific predictors for high-risk pregnancy and for targeting/customized therapy to those most likely to benefit.


  1. Top of page
  2. Abstract
  3. Introduction
  4. Antiphospholipid antibody manifestation in women with RPL
  5. Immunopathology of APS
  6. Placental pathology and micro-angiopathy induced by aPL
  7. Role of aspirin and heparin in aPL-mediated immunopathology
  8. Anticoagulation treatment in women with aPL and RPL
  9. Should treatment be different based on aPL titer, isotype, single, or multiple epitopes?
  10. Non-anticoagulant treatment for women with aPL and RPL
  11. Conclusion
  12. References
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