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Is placental haemostasis relevant to recurrent implantation failure?
Thrombosis Research 127 Suppl. 3 (2011) S93–S95
Contents lists available at ScienceDirect
Thrombosis Research j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / t h r o m r e s
Is placental haemostasis relevant to recurrent implantation failure? Scott M. Nelson* Centre for Population and Health Sciences, University of Glasgow, UK
article info Keywords: Placental haemostasis Embryo wastage Recurrent implantation failure Thrombophilia
Successful pregnancy requires the implantation of a developmentally competent embryo into a receptive endometrium. In many species, pregnancy is readily achieved and maintained. In contrast in humans, monthly fecundity rates compared to other mammalian species is relatively low at approximately 20% [1]. In addition to this relative subfertility the incidence of embryo wastage and pregnancy loss is extraordinarily high in humans, estimated to be at least 30% prior to spontaneous conception, a further 30% before 6 weeks gestation and 10% of clinical pregnancies, mostly prior to 12 weeks gestation [1]. Even in assisted conception cycles, where embryos are created and transferred a potentially even greater proportion of IVF cycles result in implantation failure. Notably the clinical pregnancy rates (CPRs) per embryo transfer in Europe for the year 2006 were 32.4% [2], meaning that 67.6% of embryos failed to implant adequately. Similarly the respective report of the Centers for Disease Control and Prevention (CDC), demonstrated an average live-birth rate per embryo transfer in the United States of America for the year 2006 of 35%. Furthermore the percentage distribution of women with a history of one or more previous failures undergoing a new IVF cycle was 34.3, 44.8, 49.6, 53.3, and 58.1% for the age groups <35, 35–37 [3], 38–40, 41–42, and >42 years, respectively, reflecting the emerging problem of repeated implantation failures (RIFs). Unfortunately there is no clear consensus regarding the definition of recurrent implantation failure. For some groups it is an unsuccessful patient with more than ten good quality embryos transferred in subsequent cycles [4]. This definition may seem too loose, according to the actual method of practice. Thus, we can consider that if a patient has undergone three good quality embryos if she is <37 years old, or two good quality embryo transfer if she is ≥37, extended investigation is required (Table 1). Consequently although numerous anatomical, endocrine, immunological, thrombophilic and genetic perturbations have been * Correspondence: Professor Scott M. Nelson. University of Glasgow, Level 2 McGregor Building, Western Infirmary, Glasgow, G12 8QQ, UK. Tel.: +44 141 211 2329; fax: +44 141 552 0873. E-mail address: [email protected] (S.M. Nelson). 0049-3848 /$ – see front matter © 2011 Elsevier Ltd. All rights reserved.
Table 1 Different conditions that may cause implantation failure Decreased endometrial receptivity Altered endocrine milieu Inadequate endometrial development Undiagnosed uterine pathology Cytokine dysregulation Embryonic factors Chromosomal abnormalities Embryo fragmentation Zona pellucida hardening Embryo/maternal synchrony Maternal conditions Autoantibodies Thrombophilias Endometriosis Hydrosalpinges Leiomyomas Difficult embryo transfer Psychological stress Reproduced with permission from Garcia-Velasco JA, et al. Implantation Failure. In: Macklon NS, Greer IA, Steegers EAP, editors, Textbook of Periconceptional Medicine. Informa UK Ltd; 2009.
invoked to explain non-chromosal miscarriage or implantation failure, none of these are specific or prevalent [5]. Within the context of recurrent miscarriage and placental haemostasis the focus has largely been on the contribution of genetic and acquired thrombophilias. This fascination reflected the epidemiological associations of thrombophilia with pregnancy loss [6,7], early studies where anti-thrombotics were effective interventions [8–10] and recognition that the coagulation cascade could have a detrimental impact on the developing trophoblast independent of conventional thrombotic mechanisms [11,12]. The
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suggestion that the positive effects of heparin and aspirin may be due to non-haemostatic effects on the trophoblast concurrently led to intervention studies in women with just the clinical phenotype of recurrent miscarriage [13,14] or with an underlying thrombophilia [13–16]. Unfortunately all of these well conducted recent trials have not shown a benefit of anti-thrombotic therapy for recurrent miscarriage [17]. Although inevitably there may be questions over the inclusion criteria, type, dose and timing of agents, it does suggest that either these agents are ineffective at targeting the pathological pathways or alternative mechanisms may underlie the previously observed associations [18]. With respect to recurrent implantation failure although the literature is not as substantive as that of the recurrent pregnancy loss field, collectively the data again suggests that thrombophilia is associated with repeated ART failure. Although the contribution of any single thrombophilia to implantation failure is likely to be small, it is likely that for any given individual, this association will reflect the total number of mutations rather than the involvement of specific genes. Specifically Azem et al. showed a significantly higher prevalance of thrombophilias in women with four or more failed IVF cycles when compared with spontaneous conceptions (OR 3.6, 95% 1.25–10.6), or women who conceived after their first cycle (OR 2.9, 95% CI 1.02–8.4) [19]. Coulam et al. demonstrated that more than three mutations were present in 74% of women with implantation failure compared to 20% of controls [20]. Qublan et al. also described a prevalence of combined thrombophilia of 35.6% in women with at least three failed IVF cycles, which is significantly higher than healthy controls, who have levels as low as 3% [21]. Lastly Bellver demonstrated a similar high prevalence of thrombophilia (46.2%) in women with recurrent implantation failure [22], confirming that some thrombophilias and especially combined thrombophilias may undermine the possibility of embryo implantation after ART. The mechanisms underlying these associations are less clear, in part due to the limited knowledge regarding the earliest stages of human implantation. The human blastocyst implants with the polar trophoectoderm overlying the inner cell mass establishing the initial contact with the uterine epithelial cells on day 5 postconception. These trophoectoderm cells undergo local differentiation, with the formation of an ouer syncytial layer and an underlying layer of mononucleate cytotrophoblast progenitor cells. These events have been recreated in vitro, where it can be observed that tongues of syncytiotrophoblast penetrate between the endometrial cells rather than engulfing them or stimulating apoptosis [23]. Gradually as the conceptus moves into the superficial endometrium the layer of syncytiotrophoblast extends over the whole surface forming a complete mantle. By day 8 postconception spaces begin to appear within the mantle, forming a series of lacunae separated by trabeculae of syncytiotrophoblast. As the mantle expands it encroaches upon the capillary network and upon the ducts of the endometrial glands [24]. The capillaries show localised dilatation in the vicinity of the conceptus, possibly hormonally induced, and connections are soon established with the lacunae, as evidenced by the appearance of erythrocytes [25]. By day 12 postconception the cytotrophoblast cells at the base of the trabeculae proliferate and penetrate into the mantle, reaching the tips of the trabeculae at approximately day 14 postconception. Given that women with recurrent implantation failure don’t have detectable hCG, which with current sensitive assays can be positive several days prior to the onset of menstruation, it is clear that the above sequence of events is being disrupted very early. Thrombophilias would therefore need to impact on the ability of the endometrium to develop adequately, communicate effectively with the embryo, or potentially disrupt the early interactions with the maternal circulation. Furthermore any intervention would need to begin at the time of embryo transfer or even earlier.
Given the historical data on the positive effect of LMWH for recurrent pregnancy loss, a similar therapeutic approach has been adopted as an intervention for recurrent implantation failure. A series of small cohort studies and trials have been reported with all commencing LMWH at the time of embryo transfer or before [26–32]. All of these studies suggest a positive effect, with the best of these a small (n = 83) placebo controlled RCT demonstrated that enoxaparin 40 mg/day was associated with a significant improvement in live birth in the heparin-treated group compared with placebo (23.8% vs. 2.8%, respectively; p < 0.05) [27]. It is clear that further substantive studies would be required to confirm or refute these observations, and whether LMWH is impacting directly on trophoblast invasion [11,12,33–36] or the process of decidualisation [37,38] remains unclear. Inevitably it may be quite different from recurrent pregnancy loss as those women had at least achieved a positive pregnancy test. Implantation is still the black box in reproductive medicine, improving implantation, especially in those couples with repeated implantation failure – a very vulnerable group [39] – is a major challenge for physicians. Exclusion of reversible causes is essential, but the recent lessons learnt from LMWH and unexplained recurrent miscarriage should be heeded. Clinical trials are desperately needed for recurrent implantation failure to ensure that we are not exposing women unnecessarily to ineffective therapies. Conflict of Interest Statement The author has no conflicts of interest. References [1] Evers JL. Female subfertility. Lancet 2002;360:151–9. [2] de Mouzon J, Goossens V, Bhattacharya S, Castilla JA, Ferraretti AP, Korsak V, et al. Assisted reproductive technology in Europe, 2006: results generated from European registers by ESHRE. Hum Reprod 2010;25:1851–62. [3] CDC, Medicine ASfR, Technology SfAR. 2006 assisted reproductive technology success rates. Atlanta: CDC; 2008. [4] Tan BK, Vandekerckhove P, Kennedy R, Keay SD. Investigation and current management of recurrent IVF treatment failure in the UK. BJOG 2005;112: 773–80. [5] Jauniaux E, Farquharson RG, Christiansen OB, Exalto N. Evidence-based guidelines for the investigation and medical treatment of recurrent miscarriage. Hum Reprod 2006;21:2216–22. [6] Robertson L, Wu O, Langhorne P, Twaddle S, Clark P, Lowe GD, et al. Thrombophilia in pregnancy: a systematic review. Br J Haematol 2006;132: 171–96. [7] Rey E, Kahn SR, David M, Shrier I. Thrombophilic disorders and fetal loss: a meta-analysis. Lancet 2003;361:901–8. [8] Rai R, Cohen H, Dave M, Regan L. Randomised controlled trial of aspirin and aspirin plus heparin in pregnant women with recurrent miscarriage associated with phospholipid antibodies (or antiphospholipid antibodies). BMJ 1997;314: 253–7. [9] Brenner B, Bar J, Ellis M, Yarom I, Yohai D, Samueloff A. Effects of enoxaparin on late pregnancy complications and neonatal outcome in women with recurrent pregnancy loss and thrombophilia: results from the Live-Enox study. Fertil Steril 2005;84:770–3. [10] Deligiannidis A, Parapanissiou E, Mavridis P, Tabakoudis G, Mavroudi A, Papastavrou T, et al. Thrombophilia and antithrombotic therapy in women with recurrent spontaneous abortions. J Reprod Med 2007;52:499–502. [11] Quenby S, Mountfield S, Cartwright JE, Whitley GSJ, Vince G. Effects of lowmolecular-weight and unfractionated heparin on trophoblast function. Obstet Gynecol 2004;104:354–61. [12] Nelson SM, Greer IA. The potential role of heparin in assisted conception. Hum Reprod Update 2008;14:623–45. [13] Kaandorp SP, Goddijn M, van der Post JA, Hutten BA, Verhoeve HR, Hamulyak K, et al. Aspirin plus heparin or aspirin alone in women with recurrent miscarriage. N Engl J Med 2010;362:1586–96. [14] Clark P, Walker ID, Langhorne P, Crichton L, Thomson A, Greaves M, et al. SPIN (Scottish Pregnancy Intervention) study: a multicenter, randomized controlled trial of low-molecular-weight heparin and low-dose aspirin in women with recurrent miscarriage. Blood 2010;115:4162–7. [15] Laskin CA, Spitzer KA, Clark CA, Crowther MR, Ginsberg JS, Hawker GA, et al. Low molecular weight heparin and aspirin for recurrent pregnancy loss: results from the randomized, controlled HepASA Trial. J Rheumatol 2009;36:279–87.
S.M. Nelson / Thrombosis Research 127 (2011) S93–S95 [16] Farquharson RG, Quenby S, Greaves M. Antiphospholipid syndrome in pregnancy: a randomized, controlled trial of treatment. Obstet Gynecol 2002;100:408–13. [17] Mantha S, Bauer KA, Zwicker JI. Low molecular weight heparin to achieve live birth following unexplained pregnancy loss: a systematic review. J Thromb Haemost 2010;8:263–8. [18] Greer IA. Antithrombotic therapy for recurrent miscarriage? N Engl J Med 2010; 362:1630–1. [19] Azem F, Many A, Yovel I, Amit A, Lessing JB, Kupferminc MJ. Increased rates of thrombophilia in women with repeated IVF failures. Hum Reprod 2004;19: 368–70. [20] Coulam CB, Jeyendran RS, Fishel LA, Roussev R. Multiple thrombophilic gene mutations are risk factors for implantation failure. Reprod BioMed Online 2006; 12:322–7. [21] Qublan HS, Eid SS, Ababneh HA, Amarin ZO, Smadi AZ, Al-Khafaji FF, et al. Acquired and inherited thrombophilia: implication in recurrent IVF and embryo transfer failure. Hum Reprod 2006;21:2694–8. [22] Bellver J, Soares SR, Alvarez C, Munoz E, Ramirez A, Rubio C, et al. The role of thrombophilia and thyroid autoimmunity in unexplained infertility, implantation failureand recurrent spontaneous abortion. Hum Reprod 2008:23(2):278–84. [23] Lindenberg S, Hyttel P, Sjøgren A, Greve T. A comparative study of attachment of human, bovine and mouse blastocysts to uterine epithelial monolayer. Hum Reprod 1989;4:446–56. [24] Hamilton WJ, Gladstone RJ. A presomite human embryo (Shaw): the implantation. J Anat 1942;76:187–203. [25] Adams EC, Hertig AT, Rock J. A description of 34 human ova within the first 17 days of development. Am J Anat 1956;98:435–93. [26] Sharif KW, Ghunaim S. Management of 273 cases of recurrent implantation failure: results of a combined evidence-based protocol. Reprod BioMed Online 2010;21:373–80. [27] Qublan H, Amarin Z, Dabbas M, Farraj AE, Beni-Merei Z, Al-Akash H, et al. Low-molecular-weight heparin in the treatment of recurrent IVF-ET failure and thrombophilia: A prospective randomized placebo-controlled trial. Hum Fertil 2008;11:246–53. [28] Kutteh WH, Yetman DL, Chantilis SJ, Crain J. Effect of antiphospholipid antibodies in women undergoing in-vitro fertilization: role of heparin and aspirin. Hum Reprod 1997;12:1171–5. [29] Schenk LM, Butler L, Morris JP, Cox B, Lecte J, Abuhamed A, et al. Heparin
[30]
[31]
[32]
[33]
[34]
[35]
[36]
[37]
[38]
[39]
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and aspiring treatment yield higher implantation rates in IVF patients with antiphospholipid antibody seropositivity compared to untreated seronegative patients. American Society for Reproductive Medicine; 1996. Sher G, Feinman M, Zouves C, Kuttner G, Maassarani G, Salem R, et al. Immunology: High fecundity rates following in-vitro fertilization and embryo transfer in antiphospholipid antibody seropositive women treated with heparin and aspirin. Hum Reprod 1994;9:2278–83. Sher G, Matzner W, Feinman M, Maassarani G, Zouves C, Chong P, et al. The selective use of heparin/aspirin therapy, alone or in combination with intravenous immunoglobulin G, in the management of antiphospholipid antibody-positive women undergoing in vitro fertilization. Am J Reprod Immunol 1998;40:74–82. Stern C, Chamley L, Norris H, Hale L, Baker HW. A randomized, doubleblind, placebo-controlled trial of heparin and aspirin for women with in vitro fertilization implantation failure and antiphospholipid or antinuclear antibodies. Fertil Steril 2003;80:376–83. Di Simone N, Di Nicuolo F, Sanguinetti M, Ferrazzani S, D’Alessio MC, Castellani R, et al. Low-molecular weight heparin induces in vitro trophoblast invasiveness: role of matrix metalloproteinases and tissue inhibitors. Placenta 2007;28:298–304. Ganapathy R, Whitley GSJ, Cartwright JE, Dash PR, Thilaganathan B. Effect of heparin and fractionated heparin on trophoblast invasion. Hum Reprod 2007; 22:2523–7. Erden O, Imir A, Guvenal T, Muslehiddinoglu A, Arici S, Cetin M, et al. Investigation of the effects of heparin and low molecular weight heparin on E-cadherin and laminin expression in rat pregnancy by immunohistochemistry. Hum Reprod 2006;21:3014–8. Bose P, Black S, Kadyrov M, Weissenborn U, Neulen J, Regan L, et al. Heparin and aspirin attenuate placental apoptosis in vitro: Implications for early pregnancy failure. Am J Obstet Gynecol 2005;192:23–30. Chobotova K, Karpovich N, Carver J, Manek S, Gullick WJ, Barlow DH, et al. Heparin-binding epidermal growth factor and its receptors mediate decidualization and potentiate survival of human endometrial stromal cells. J Clin Endocrinol Metab 2005;90:913–9. Fluhr H, Spratte J, Ehrhardt J, Steinmuller F, Licht P, Zygmunt M. Heparin and low-molecular-weight heparins modulate the decidualization of human endometrial stromal cells. Fertil Steril 2010;93:2581–7. Nap AW, Evers JL. Couples with infertility belong to a very vulnerable group, they should not be exploited. Hum Reprod 2007;22:3262–3; author reply: 3.
Contents lists available at ScienceDirect
Thrombosis Research j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / t h r o m r e s
Is placental haemostasis relevant to recurrent implantation failure? Scott M. Nelson* Centre for Population and Health Sciences, University of Glasgow, UK
article info Keywords: Placental haemostasis Embryo wastage Recurrent implantation failure Thrombophilia
Successful pregnancy requires the implantation of a developmentally competent embryo into a receptive endometrium. In many species, pregnancy is readily achieved and maintained. In contrast in humans, monthly fecundity rates compared to other mammalian species is relatively low at approximately 20% [1]. In addition to this relative subfertility the incidence of embryo wastage and pregnancy loss is extraordinarily high in humans, estimated to be at least 30% prior to spontaneous conception, a further 30% before 6 weeks gestation and 10% of clinical pregnancies, mostly prior to 12 weeks gestation [1]. Even in assisted conception cycles, where embryos are created and transferred a potentially even greater proportion of IVF cycles result in implantation failure. Notably the clinical pregnancy rates (CPRs) per embryo transfer in Europe for the year 2006 were 32.4% [2], meaning that 67.6% of embryos failed to implant adequately. Similarly the respective report of the Centers for Disease Control and Prevention (CDC), demonstrated an average live-birth rate per embryo transfer in the United States of America for the year 2006 of 35%. Furthermore the percentage distribution of women with a history of one or more previous failures undergoing a new IVF cycle was 34.3, 44.8, 49.6, 53.3, and 58.1% for the age groups <35, 35–37 [3], 38–40, 41–42, and >42 years, respectively, reflecting the emerging problem of repeated implantation failures (RIFs). Unfortunately there is no clear consensus regarding the definition of recurrent implantation failure. For some groups it is an unsuccessful patient with more than ten good quality embryos transferred in subsequent cycles [4]. This definition may seem too loose, according to the actual method of practice. Thus, we can consider that if a patient has undergone three good quality embryos if she is <37 years old, or two good quality embryo transfer if she is ≥37, extended investigation is required (Table 1). Consequently although numerous anatomical, endocrine, immunological, thrombophilic and genetic perturbations have been * Correspondence: Professor Scott M. Nelson. University of Glasgow, Level 2 McGregor Building, Western Infirmary, Glasgow, G12 8QQ, UK. Tel.: +44 141 211 2329; fax: +44 141 552 0873. E-mail address: [email protected] (S.M. Nelson). 0049-3848 /$ – see front matter © 2011 Elsevier Ltd. All rights reserved.
Table 1 Different conditions that may cause implantation failure Decreased endometrial receptivity Altered endocrine milieu Inadequate endometrial development Undiagnosed uterine pathology Cytokine dysregulation Embryonic factors Chromosomal abnormalities Embryo fragmentation Zona pellucida hardening Embryo/maternal synchrony Maternal conditions Autoantibodies Thrombophilias Endometriosis Hydrosalpinges Leiomyomas Difficult embryo transfer Psychological stress Reproduced with permission from Garcia-Velasco JA, et al. Implantation Failure. In: Macklon NS, Greer IA, Steegers EAP, editors, Textbook of Periconceptional Medicine. Informa UK Ltd; 2009.
invoked to explain non-chromosal miscarriage or implantation failure, none of these are specific or prevalent [5]. Within the context of recurrent miscarriage and placental haemostasis the focus has largely been on the contribution of genetic and acquired thrombophilias. This fascination reflected the epidemiological associations of thrombophilia with pregnancy loss [6,7], early studies where anti-thrombotics were effective interventions [8–10] and recognition that the coagulation cascade could have a detrimental impact on the developing trophoblast independent of conventional thrombotic mechanisms [11,12]. The
S94
S.M. Nelson / Thrombosis Research 127 (2011) S93–S95
suggestion that the positive effects of heparin and aspirin may be due to non-haemostatic effects on the trophoblast concurrently led to intervention studies in women with just the clinical phenotype of recurrent miscarriage [13,14] or with an underlying thrombophilia [13–16]. Unfortunately all of these well conducted recent trials have not shown a benefit of anti-thrombotic therapy for recurrent miscarriage [17]. Although inevitably there may be questions over the inclusion criteria, type, dose and timing of agents, it does suggest that either these agents are ineffective at targeting the pathological pathways or alternative mechanisms may underlie the previously observed associations [18]. With respect to recurrent implantation failure although the literature is not as substantive as that of the recurrent pregnancy loss field, collectively the data again suggests that thrombophilia is associated with repeated ART failure. Although the contribution of any single thrombophilia to implantation failure is likely to be small, it is likely that for any given individual, this association will reflect the total number of mutations rather than the involvement of specific genes. Specifically Azem et al. showed a significantly higher prevalance of thrombophilias in women with four or more failed IVF cycles when compared with spontaneous conceptions (OR 3.6, 95% 1.25–10.6), or women who conceived after their first cycle (OR 2.9, 95% CI 1.02–8.4) [19]. Coulam et al. demonstrated that more than three mutations were present in 74% of women with implantation failure compared to 20% of controls [20]. Qublan et al. also described a prevalence of combined thrombophilia of 35.6% in women with at least three failed IVF cycles, which is significantly higher than healthy controls, who have levels as low as 3% [21]. Lastly Bellver demonstrated a similar high prevalence of thrombophilia (46.2%) in women with recurrent implantation failure [22], confirming that some thrombophilias and especially combined thrombophilias may undermine the possibility of embryo implantation after ART. The mechanisms underlying these associations are less clear, in part due to the limited knowledge regarding the earliest stages of human implantation. The human blastocyst implants with the polar trophoectoderm overlying the inner cell mass establishing the initial contact with the uterine epithelial cells on day 5 postconception. These trophoectoderm cells undergo local differentiation, with the formation of an ouer syncytial layer and an underlying layer of mononucleate cytotrophoblast progenitor cells. These events have been recreated in vitro, where it can be observed that tongues of syncytiotrophoblast penetrate between the endometrial cells rather than engulfing them or stimulating apoptosis [23]. Gradually as the conceptus moves into the superficial endometrium the layer of syncytiotrophoblast extends over the whole surface forming a complete mantle. By day 8 postconception spaces begin to appear within the mantle, forming a series of lacunae separated by trabeculae of syncytiotrophoblast. As the mantle expands it encroaches upon the capillary network and upon the ducts of the endometrial glands [24]. The capillaries show localised dilatation in the vicinity of the conceptus, possibly hormonally induced, and connections are soon established with the lacunae, as evidenced by the appearance of erythrocytes [25]. By day 12 postconception the cytotrophoblast cells at the base of the trabeculae proliferate and penetrate into the mantle, reaching the tips of the trabeculae at approximately day 14 postconception. Given that women with recurrent implantation failure don’t have detectable hCG, which with current sensitive assays can be positive several days prior to the onset of menstruation, it is clear that the above sequence of events is being disrupted very early. Thrombophilias would therefore need to impact on the ability of the endometrium to develop adequately, communicate effectively with the embryo, or potentially disrupt the early interactions with the maternal circulation. Furthermore any intervention would need to begin at the time of embryo transfer or even earlier.
Given the historical data on the positive effect of LMWH for recurrent pregnancy loss, a similar therapeutic approach has been adopted as an intervention for recurrent implantation failure. A series of small cohort studies and trials have been reported with all commencing LMWH at the time of embryo transfer or before [26–32]. All of these studies suggest a positive effect, with the best of these a small (n = 83) placebo controlled RCT demonstrated that enoxaparin 40 mg/day was associated with a significant improvement in live birth in the heparin-treated group compared with placebo (23.8% vs. 2.8%, respectively; p < 0.05) [27]. It is clear that further substantive studies would be required to confirm or refute these observations, and whether LMWH is impacting directly on trophoblast invasion [11,12,33–36] or the process of decidualisation [37,38] remains unclear. Inevitably it may be quite different from recurrent pregnancy loss as those women had at least achieved a positive pregnancy test. Implantation is still the black box in reproductive medicine, improving implantation, especially in those couples with repeated implantation failure – a very vulnerable group [39] – is a major challenge for physicians. Exclusion of reversible causes is essential, but the recent lessons learnt from LMWH and unexplained recurrent miscarriage should be heeded. Clinical trials are desperately needed for recurrent implantation failure to ensure that we are not exposing women unnecessarily to ineffective therapies. Conflict of Interest Statement The author has no conflicts of interest. References [1] Evers JL. Female subfertility. Lancet 2002;360:151–9. [2] de Mouzon J, Goossens V, Bhattacharya S, Castilla JA, Ferraretti AP, Korsak V, et al. Assisted reproductive technology in Europe, 2006: results generated from European registers by ESHRE. Hum Reprod 2010;25:1851–62. [3] CDC, Medicine ASfR, Technology SfAR. 2006 assisted reproductive technology success rates. Atlanta: CDC; 2008. [4] Tan BK, Vandekerckhove P, Kennedy R, Keay SD. Investigation and current management of recurrent IVF treatment failure in the UK. BJOG 2005;112: 773–80. [5] Jauniaux E, Farquharson RG, Christiansen OB, Exalto N. Evidence-based guidelines for the investigation and medical treatment of recurrent miscarriage. Hum Reprod 2006;21:2216–22. [6] Robertson L, Wu O, Langhorne P, Twaddle S, Clark P, Lowe GD, et al. Thrombophilia in pregnancy: a systematic review. Br J Haematol 2006;132: 171–96. [7] Rey E, Kahn SR, David M, Shrier I. Thrombophilic disorders and fetal loss: a meta-analysis. Lancet 2003;361:901–8. [8] Rai R, Cohen H, Dave M, Regan L. Randomised controlled trial of aspirin and aspirin plus heparin in pregnant women with recurrent miscarriage associated with phospholipid antibodies (or antiphospholipid antibodies). BMJ 1997;314: 253–7. [9] Brenner B, Bar J, Ellis M, Yarom I, Yohai D, Samueloff A. Effects of enoxaparin on late pregnancy complications and neonatal outcome in women with recurrent pregnancy loss and thrombophilia: results from the Live-Enox study. Fertil Steril 2005;84:770–3. [10] Deligiannidis A, Parapanissiou E, Mavridis P, Tabakoudis G, Mavroudi A, Papastavrou T, et al. Thrombophilia and antithrombotic therapy in women with recurrent spontaneous abortions. J Reprod Med 2007;52:499–502. [11] Quenby S, Mountfield S, Cartwright JE, Whitley GSJ, Vince G. Effects of lowmolecular-weight and unfractionated heparin on trophoblast function. Obstet Gynecol 2004;104:354–61. [12] Nelson SM, Greer IA. The potential role of heparin in assisted conception. Hum Reprod Update 2008;14:623–45. [13] Kaandorp SP, Goddijn M, van der Post JA, Hutten BA, Verhoeve HR, Hamulyak K, et al. Aspirin plus heparin or aspirin alone in women with recurrent miscarriage. N Engl J Med 2010;362:1586–96. [14] Clark P, Walker ID, Langhorne P, Crichton L, Thomson A, Greaves M, et al. SPIN (Scottish Pregnancy Intervention) study: a multicenter, randomized controlled trial of low-molecular-weight heparin and low-dose aspirin in women with recurrent miscarriage. Blood 2010;115:4162–7. [15] Laskin CA, Spitzer KA, Clark CA, Crowther MR, Ginsberg JS, Hawker GA, et al. Low molecular weight heparin and aspirin for recurrent pregnancy loss: results from the randomized, controlled HepASA Trial. J Rheumatol 2009;36:279–87.
S.M. Nelson / Thrombosis Research 127 (2011) S93–S95 [16] Farquharson RG, Quenby S, Greaves M. Antiphospholipid syndrome in pregnancy: a randomized, controlled trial of treatment. Obstet Gynecol 2002;100:408–13. [17] Mantha S, Bauer KA, Zwicker JI. Low molecular weight heparin to achieve live birth following unexplained pregnancy loss: a systematic review. J Thromb Haemost 2010;8:263–8. [18] Greer IA. Antithrombotic therapy for recurrent miscarriage? N Engl J Med 2010; 362:1630–1. [19] Azem F, Many A, Yovel I, Amit A, Lessing JB, Kupferminc MJ. Increased rates of thrombophilia in women with repeated IVF failures. Hum Reprod 2004;19: 368–70. [20] Coulam CB, Jeyendran RS, Fishel LA, Roussev R. Multiple thrombophilic gene mutations are risk factors for implantation failure. Reprod BioMed Online 2006; 12:322–7. [21] Qublan HS, Eid SS, Ababneh HA, Amarin ZO, Smadi AZ, Al-Khafaji FF, et al. Acquired and inherited thrombophilia: implication in recurrent IVF and embryo transfer failure. Hum Reprod 2006;21:2694–8. [22] Bellver J, Soares SR, Alvarez C, Munoz E, Ramirez A, Rubio C, et al. The role of thrombophilia and thyroid autoimmunity in unexplained infertility, implantation failureand recurrent spontaneous abortion. Hum Reprod 2008:23(2):278–84. [23] Lindenberg S, Hyttel P, Sjøgren A, Greve T. A comparative study of attachment of human, bovine and mouse blastocysts to uterine epithelial monolayer. Hum Reprod 1989;4:446–56. [24] Hamilton WJ, Gladstone RJ. A presomite human embryo (Shaw): the implantation. J Anat 1942;76:187–203. [25] Adams EC, Hertig AT, Rock J. A description of 34 human ova within the first 17 days of development. Am J Anat 1956;98:435–93. [26] Sharif KW, Ghunaim S. Management of 273 cases of recurrent implantation failure: results of a combined evidence-based protocol. Reprod BioMed Online 2010;21:373–80. [27] Qublan H, Amarin Z, Dabbas M, Farraj AE, Beni-Merei Z, Al-Akash H, et al. Low-molecular-weight heparin in the treatment of recurrent IVF-ET failure and thrombophilia: A prospective randomized placebo-controlled trial. Hum Fertil 2008;11:246–53. [28] Kutteh WH, Yetman DL, Chantilis SJ, Crain J. Effect of antiphospholipid antibodies in women undergoing in-vitro fertilization: role of heparin and aspirin. Hum Reprod 1997;12:1171–5. [29] Schenk LM, Butler L, Morris JP, Cox B, Lecte J, Abuhamed A, et al. Heparin
[30]
[31]
[32]
[33]
[34]
[35]
[36]
[37]
[38]
[39]
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and aspiring treatment yield higher implantation rates in IVF patients with antiphospholipid antibody seropositivity compared to untreated seronegative patients. American Society for Reproductive Medicine; 1996. Sher G, Feinman M, Zouves C, Kuttner G, Maassarani G, Salem R, et al. Immunology: High fecundity rates following in-vitro fertilization and embryo transfer in antiphospholipid antibody seropositive women treated with heparin and aspirin. Hum Reprod 1994;9:2278–83. Sher G, Matzner W, Feinman M, Maassarani G, Zouves C, Chong P, et al. The selective use of heparin/aspirin therapy, alone or in combination with intravenous immunoglobulin G, in the management of antiphospholipid antibody-positive women undergoing in vitro fertilization. Am J Reprod Immunol 1998;40:74–82. Stern C, Chamley L, Norris H, Hale L, Baker HW. A randomized, doubleblind, placebo-controlled trial of heparin and aspirin for women with in vitro fertilization implantation failure and antiphospholipid or antinuclear antibodies. Fertil Steril 2003;80:376–83. Di Simone N, Di Nicuolo F, Sanguinetti M, Ferrazzani S, D’Alessio MC, Castellani R, et al. Low-molecular weight heparin induces in vitro trophoblast invasiveness: role of matrix metalloproteinases and tissue inhibitors. Placenta 2007;28:298–304. Ganapathy R, Whitley GSJ, Cartwright JE, Dash PR, Thilaganathan B. Effect of heparin and fractionated heparin on trophoblast invasion. Hum Reprod 2007; 22:2523–7. Erden O, Imir A, Guvenal T, Muslehiddinoglu A, Arici S, Cetin M, et al. Investigation of the effects of heparin and low molecular weight heparin on E-cadherin and laminin expression in rat pregnancy by immunohistochemistry. Hum Reprod 2006;21:3014–8. Bose P, Black S, Kadyrov M, Weissenborn U, Neulen J, Regan L, et al. Heparin and aspirin attenuate placental apoptosis in vitro: Implications for early pregnancy failure. Am J Obstet Gynecol 2005;192:23–30. Chobotova K, Karpovich N, Carver J, Manek S, Gullick WJ, Barlow DH, et al. Heparin-binding epidermal growth factor and its receptors mediate decidualization and potentiate survival of human endometrial stromal cells. J Clin Endocrinol Metab 2005;90:913–9. Fluhr H, Spratte J, Ehrhardt J, Steinmuller F, Licht P, Zygmunt M. Heparin and low-molecular-weight heparins modulate the decidualization of human endometrial stromal cells. Fertil Steril 2010;93:2581–7. Nap AW, Evers JL. Couples with infertility belong to a very vulnerable group, they should not be exploited. Hum Reprod 2007;22:3262–3; author reply: 3.