- Email: [email protected]
Recurrent miscarriage
ARTICLE IN PRESS Current Obstetrics & Gynaecology (2004) 14, 247–253
www.elsevier.com/cuog
Recurrent miscarriage Feroza Dawood, Roy Farquharson*, Siobhan Quenby University Department of Obstetrics and Gynaecology, Liverpool Women’s Hospital, Crown Street, Liverpool L8 7SS, UK
KEYWORDS Embryo losses; Fetal losses; Antiphospholipod syndrome; Cytogenetics; Thrombophilia
Summary Recurrent miscarriage (RM) is a challenging clinical condition accentuated by a multi-factorial aetiology. Recent research has afforded us an in-depth understanding of the complexities of the evolving pregnancy and of the potential hazards that it may face at different developmental stages. A delineation of types of pregnancy loss provides a useful framework in the management of RM. New theories have highlighted the impact of a hostile endometrium, chromosomal aberrations, abnormal immune responses and hormonal influences on recurrent pregnancy loss. Whilst the antiphospholipid syndrome retains its importance as a significant aetiology in RM, recent attention has focused on the role of other hereditary and acquired thrombophilias. As far as mid-trimester losses are concerned, the entities of cervical weakness and bacterial vaginosis are prominent features. & 2004 Elsevier Ltd. All rights reserved.
Introduction
Diagnostic categories
Recurrent miscarriage (RM) is defined as three or more consecutive pregnancy losses prior to 24 weeks of gestation. As spontaneous miscarriage complicates 15–20% of all pregnancies, by probability alone the recurrent miscarriage rate should be in the order of 0.15 ¼ 0.3–0.4%. Rather, the actual rate is much higher at 1–2%, supporting the assumption that specific underlying pathologies exist. The definition of RM traverses a wide gestational range and since various pathophysiological processes may be inflicted in different stages of pregnancy, a fundamental tool in the management of RM is to stratify the type of pregnancy loss. A suggestion of pregnancy loss classification is set out below (Table 1).
Several previously lauded theories and associations of RM have been discredited and superseded by a modern, refined and evidence-based approach. As a consequence there has been a radical shift in the investigative algorithm of recurrent miscarriage. Recent research has questioned the value of routine screening for underlying diabetes and thyroid disease in asymptomatic patients, as the prevalence of these endocrinopathies have been found to be similar in women with RM and the general population. Routine screening for toxoplasmosis, rubella, cytomegalovirus and herpes simplex virus (TORCH) is also currently deemed unnecessary. A suggested algorithm of targeted investigations, ideally based on the type of previous pregnancy losses, is outlined below (Table 2). However, one should remain cognisant that the heterogenous nature of RM implies that there may well be a convergence of aetiologies in the clinical setting. Consequently, meticulous history taking and a practical approach is mandatory.
*Corresponding author. Tel.: þ 44-151-702-4001/4221; fax: þ 44-151-702-4137. E-mail address: [email protected] (R. Farquharson).
0957-5847/$ - see front matter & 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.curobgyn.2004.04.007
ARTICLE IN PRESS 248
Table 1
F. Dawood et al.
Pregnancy loss classification.
Type of loss
Typical gestation (weeks)
Fetal heart activity
Pre-embryo Embryo Fetal Late fetal loss Spontaneous second trimester loss
o6 6–8 8–12 12–24 12–24
Never identified Never identified Cessation of fetal heartbeat Intrauterine death Fetal heart present, but cervical dilatation or SROMn precipitates in delivery
n
SROM (spontaneous rupture of membranes).
Table 2
Diagnostic investigations in recurrent miscarriage.
Type of miscarriage
Associated conditions
Investigations
Pre-embryonic and embryonic
Karyotype abnormalities
Parental karyotypes Cytogenetic analysis of miscarried tissue FSH, LH, Day 21 progesterone, pelvic ultrasound
Endocrine: PCOS Oligomenorrhea Endometrial abnormalities Immunological
Endometrial sampling (currently strictly research based) Dilute Russell Viper Venom Time (DRVVT) for lupus anticoagulant, anticardiolipin antibodies, IgG and IgM
Fetal (early and late)
Antiphospholipid syndrome Thrombophilia
Anticardiolipin antibodies (IgG and IgM), Lupus anticoagulant (DRVVT), activated protein C resistance, protein C & S deficiency, hyperhomocysteinaemia, factor V Leiden and prothrombin gene mutations
Spontaneous midtrimester losses
Anatomical Cervical weakness Bacterial vaginosis
Pelvic ultrasound, three-dimensional ultrasound Hysteroscopy, swabs for mycoplasma, ureaplasma and chlamydia
Embryonic losses The fate of the developing embryo is challenged at the outset of both the molecular and biological phases. At the epithelial juncture, abnormality with impairment of barrier function may lead to a situation in which ‘poor quality’ embryos that are otherwise destined to fail, implant and present later as miscarriages. The majority of miscarriages are embryonic losses. An interesting and as yet unexplained aspect of embryonic loss is the fact that the majority (90%) of pregnancies with an abnormal karyotype miscarry in the first trimester, while the majority (93%) of pregnancies with a normal karyotype continue. It appears that couples conceive a number of abnormal embryos and that this is further compounded by endometrial nonselectivity, resulting in RM. These hypotheses have
spawned a novel paradigm: the innovative concept of miscarriage as a natural process of quality control, and RM as failure of this quality control. Furthermore, immunological influences and a hostile endometrium have also been implicated in contributing to embryonic loss.
Karyotype abnormalities Parental peripheral blood karyotypes Parental peripheral blood karyotype abnormalities are reported in 3–5% of couples suffering recurrent miscarriage and testing of both partners is therefore advocated. The commonest abnormalities appear to be balanced reciprocal and Robertsonian translocations. Liaison with a clinical geneticist for genetic counselling is recommended. Pre-implantation
ARTICLE IN PRESS Recurrent miscarriage
genetic diagnosis (PGD), used to investigate women with RM, demonstrates that they produce more aneuploid embryos than normal women. When PGD is employed to discard karyotypically abnormal embryos (known as aneuploidy screening) the miscarriage rate after in vitro fertilisation (IVF) is reduced. These recent advances in IVF and PGD, as well as in fluorescent in situ hybridisation (FISH), afford couples afflicted with abnormal peripheral karyotypes a measured but conceivable form of treatment.
Cytogenetic analysis of miscarried tissue Culture and karyotyping of miscarried pregnancies from women suffering from RM have detected a 29–57% abnormality rate. Chorionic villous karyotyping, performed on prospective miscarriages following three or more pregnancy losses, revealed abnormality in 60% of cases. However, these figures may yet underestimate the actual incidence of chromosomal anomalies, as conventional cytogenetic analysis of miscarried tissue relies on culturing and karyotyping, a technique limited by external contamination, culture failure and selective growth of maternal cells. Analysis of spontaneous miscarriages by the technique of comparative genomic hybridisation (CGH) obviates the need for culture, thus improving detection of chromosomal imbalances. Although the routine cytogenetic analysis of miscarried products is not a widely adopted practice in most miscarriage clinics for pragmatic and financial reasons, there is strong empirical evidence that the introduction of these techniques will offer a more thorough evaluation of reproductive loss in the future.
Endometrial and immunological factors Recent research has highlighted the role of abnormal endometrial morphology in women with RM. There is emerging evidence of maladaptive changes in the endometriums of women with recurrent miscarriage. It has been hypothesised that the endometrium in women suffering from RM may be more receptive to implantation than in normal controls. This is thought to be mediated by compromised epithelial function. The expression of MUC1, an anti-adhesion molecule, has been found to be lower in the endometriums of women suffering from RM than in controls, and in vitro experiments have revealed that MUC1 is selectively removed from the human maternal epithelial cell
249
surface in the immediate vicinity of an attaching embryo. The maternal decidua is predominantly colonised by the uterine natural killer (NK) cell, also known as the uterine large granular lymphocyte (LGL). Increased numbers of CD56 þ LGL have been found in the pre-implantation endometriums of RM patients compared to controls. Furthermore, increased numbers of CD56 þ LGL leucocytes were found in the endometriums of patients who subsequently miscarried than in those who had live births. These observations have triggered two competing hypotheses: either CD56 þ LGL are hostile to invading trophoblast or CD56 þ LGL may facilitate the implantation of abnormal blastocysts, leading to the clinical presentation of RM. The latter interpretation is supported by recent data showing CD56 þ LGL are more numerous in the decidua of chromosomally abnormal miscarriages than in chromosomally normal miscarriages. Differences were detected in the decidua leucocytes from the miscarriages of women with unexplained RM and a normal fetal karyotype, when compared to that from women with RM and abnormal fetal karyotype. Cytokine aberrations The systemic maternal immune responses are governed by activated lymphocytes and macrophages which produce pleiotropic soluble proteins known as cytokines. During normal pregnancy immune responses may be biased in favour of a type 2 cytokine profile, and it has been suggested that RM is an abnormal type 1 response. A prospective study of the type 1/type 2 cytokine shift in early pregnancies of women suffering from RM revealed that the cytokine shift, which appears to characterise normal pregnancy, was accentuated rather than diminished in RM pregnant women. Therefore, in a RM population women may be immunologically more receptive to abnormal pregnancies. Immunomodulation There is no benefit derived from routine testing for HLA types or anti-paternal cytotoxic antibodies in an RM population. A recent systematic review analysed 19 randomised controlled trials of immunotherapy for recurrent miscarriage. The review deduced that neither paternal cell immunisation nor third party donor leukocytes provided any significant beneficial effects over placebo in preventing further miscarriage. The analysis also concluded that there was no improvement in subsequent live birth rates with the usage of
ARTICLE IN PRESS 250
trophoblast membranes and intravenous immunoglobulin compared to placebo.
Hormonal factors Although polycystic ovary syndrome (PCOS) has been reported as having a higher prevalence in RM women compared to the general population, PCOS is no longer accepted as having a significant role in the pathophysiology of RM. Another contentious issue is the belief that the treatment of lutealphase defects (progesterone deficiency induced by a malfunctioning corpus luteum) prevents pregnancy loss. There is certainly no robust evidence to justify the use of exogenous progesterone to support a pregnancy in RM patients. There is a strand of evidence supporting a causal relationship between hyperprolactinaemia and RM. However, this association requires further elucidation before any treatment options are endorsed. Oligomenorrhea The entity of oligomenorrhoea is over represented in the RM population (10–15%), in contrast to 1% in the general population. Women with oligomenorrhoea have been shown to have lower luteal phase oestradiol levels, which may alter endometrial receptivity with subsequent compromised implantation and resultant embryonic losses. The presence of oligomenorrhoea has also been shown to give a higher chance of a normal karyotype miscarriage. Although the precise role of endogenous human chorionic gonadotrophin (HCG) is not yet established, it is known that it is essential in the establishment of pregnancy. A systematic review of four trials concluded that there was insufficient evidence to evaluate the use of HCG during pregnancy to prevent miscarriage in women with a history of RM. However, there may be a case for treatment with HCG in reducing the risk of miscarriage for women with oligomenorrhoea. This needs to be expounded by randomised controlled trials.
Fetal losses Antiphospholipid syndrome (APS) The antiphospholipid syndrome (APS) remains entrenched as one of the most important causes of fetal loss. It is characterised by a clinical history of recurrent miscarriage, thrombosis or thrombocytopenia, accompanied by persistently positive tests for antiphospholipid antibodies. Tests for antiphospholipid antibodies are usually a medium to high
F. Dawood et al.
titre of antibody to cardiolipin (ACA) and/or abnormalities of coagulation-based assays that are consistent with the presence of a lupus anticoagulant and should be positive on two occasions at least 6 weeks apart. The clinical obstetric criteria to diagnose APS are *
*
*
three or more consecutive spontaneous losses before the tenth week of gestation; one or more premature births before 34 weeks due to severe pre-eclampsia or impaired fetal growth; one or more unexplained intrauterine deaths beyond 10 weeks gestation.
Thrombosis is frequently observed in the decidua and placentae of patients with APS. Indeed the underlying pathogenetic mechanism linking APS to pregnancy loss has been attributed to placental thrombosis and infarction. However, thrombosis is neither a universal nor a distinct feature of APS pregnancies. Therefore, the pathophysiological mechanisms have been extrapolated to encompass the direct effect of anticardiolipin antibodies on trophoblast invasion. Anticardiolipin antibodies have been found to directly react with trophoblast cells, preventing trophoblast proliferation. It has been discovered that ACA inhibited chemotaxis and differentiation of villous trophoblast isolated from third trimester placentae and that low-molecular weight heparin reduced the binding of ACA to trophoblast cells and restored trophoblast function. However, the clinical spectrum of disorders that are associated with ACA are more likely to be caused by placentation problems that occur in the first and second trimester than in the third trimester. ACA are associated with first and second trimester miscarriages, pre-eclampsia and intrauterine growth restriction. In pre-eclampsia and intrauterine growth restriction there are abnormalities in extravillous trophoblast (EVT) invasion. EVTs produce physiological changes in both the decidual and myometrial segments of the spiral arteries in normal pregnancy. EVT cells are a highly migratory and proliferative cell population and start to invade the decidual segments in the first trimester and the myometrial segments after 16 weeks gestation, resulting in a high flow, low impedance system. In the presence of ACA, EVT migration and invasion appears to be largely restricted to the decidual portion. The mechanisms underlying this deficient trophoblast invasion are unclear. EVTs are morphologically different from villous trophoblasts and they differ in their expression of oncogenes and adhesion molecules. Thus, the EVTs and the villous
ARTICLE IN PRESS Recurrent miscarriage
trophoblasts are likely to behave differently in in vitro models of trophoblast function. Apoptosis (programmed cell death) may be important in controlling trophoblast invasion and is involved in trophoblast cell turnover. Observations of increased placental apoptosis with advancing gestational age suggest that apoptosis is a normal placental process. Changes in the phospholipid component of the cell membrane are an integral, initial component of apoptosis. During the early stages of apoptosis, phosphatidylserine flips from the inner surface to the outer surface of the membrane. It is important to establish whether any interaction of ACA with the cell membrane alters apoptosis. The optimum treatment of RM women with APS is a subject of contention. While a combination of low-dose aspirin and heparin has been advocated by some authorities, the most recent randomised controlled trial of 98 women, representing the largest recruitment population to date, has clearly depicted no significant difference in the live birth rate of the study arm treated with low-dose aspirin alone, compared to the arm receiving a combination of low-dose aspirin and low-molecular weight heparin (72 and 78%, respectively). Hence, the routine use of heparin has come under scrutiny. While the heparin debate continues, treatment with aspirin 75 mg daily throughout pregnancy is definitely recommended in RM women with APS.
Thrombophilia Thrombophilic disorders have generated considerable interest in the field of RM. Thrombophilia is heralded by a predisposition to thrombosis due to a procoagulant state. Several blood clotting disorders are grouped under the umbrella term of thrombophilia. Amongst these, are activated protein C resistance (APCR), protein S deficiency, protein C deficiency, prothrombin mutation, antithrombin III deficiency and hyperhomocysteinaemia (methylenetetrahydrofolate reductase mutation, C677 T MTHFR). Clinical studies suggest that the underlying pathophysiological mechanism is mediated via hypercoagulation, leading to uteroplacental insufficiency with resultant pregnancy loss. The antiphospholipid syndrome, described previously, is an acquired thrombophilia with a wellestablished role in the aetiology of RM. More recently attention has focused on the significance of other genetic and acquired thrombophilias as potential putative factors in RM. Prothrombin gene mutation is signalled by a defect in clotting factor II at position G20210A. The relative
251
risk for thrombosis in patients with this mutation is two-fold in heterozygotes. Individuals with hyperhomocysteinaemia exhibit a deficiency of folate due to the presence of the methylene tetrahydrofolate reductase mutation (MTHFR C677 T). The thrombotic risk is increased two-fold in homozygosity; and in the heterozygous state for Antithrombin III deficiency, the risk is 20- to 50-fold. APCR has emerged as the commonest genetic cause of thrombo-embolism. APCR is caused by a point mutation (Factor V Leiden, FVL) in 95% of cases. Some individuals exhibit activated protein C resistance, but do not possess this mutation. This phenomenon has been termed acquired APCR; the true aetiology of which remains an enigma. The risk of thrombosis is increased 5- to 10-fold in heterozygous carriers of FVL, and 100-fold in homozygosity. Hereditary and acquired APCR have been demonstrated by several studies to be a significant risk factor for fetal loss. An increased risk of fetal loss in women with thrombophilia compared with controls was described by a European multicentre retrospective study, incorporating all known thrombophilias. The risk of stillbirth was higher in women with multiple thrombophilic defects, suggesting a synergistic effect. While some researchers would contest screening for thrombophilia in the initial evaluation of RM, the authors opine that unexplained recurrent fetal losses should prompt testing. A personal or substantial family history of thrombosis also warrants testing. It has been suggested that anticoagulation therapy significantly improves pregnancy outcome in women with thrombophilia. This is an avenue that begs further evaluation.
Mid-trimester losses Mid-trimester losses refer to miscarriages that occur between 12 and 24 weeks of gestation and constitute approximately 5% of all pregnancy losses. The presence of dual pathology occurs in 10–15% of mid-trimester losses.
Late fetal losses Antiphospholipid syndrome is one of the most important causes of late fetal losses, but testing for other thrombophilias is also warranted.
Spontaneous mid-trimester losses Anatomical The incidence of uterine anomaly is less than 5% in RM women. Although traditionally associated with
ARTICLE IN PRESS 252
mid-trimester losses, uterine abnormalities may also be implicated in first trimester losses. The use of non-invasive three-dimensional ultrasound scan is gaining vogue as it provides both diagnosis and classification of uterine malformation, rendering hysteroscopy unnecessary. Cervical weakness accounts for approximately 10% of mid-trimester losses. It may follow previous damage caused by cone biopsy, operative dilatation of the cervix, or may rarely be due to a congenital defect, presenting classically as painless dilatation of the cervix, which may then lead to spontaneous rupture of membranes. Following this specific history, a pre-conceptual confirmatory hysteroscopy is recommended to assess cervical resistance and length. These findings will dictate treatment options. In cases of confirmed cervical weakness, cervical cerclage is recommended. A randomised trial of cervical cerclage was conducted by the Royal College of Obstetricians. This trial reported a marginal reduction in the number of deliveries prior to 33 weeks in the cerclage group. The current recommendation is the use of transvaginal cerclage in high-risk women, for example those with a history of three or more mid-trimester losses. In a small number of clinical cases, women experience intractable mid-trimester losses refractory to transvaginal cerclage. It is in this select group of women that transabdominal cerclage is the only remaining hope of a successful outcome. Patient selection is crucial as this intervention is not without associated complications such as iatrogenic miscarriage, uterine rupture and rarely, hysterectomy. Transabdominal suture insertion is usually undertaken at 10 weeks of gestation and subsequent delivery by elective Caesarean section is mandatory. What is certainly warranted is a randomised controlled trial with two arms evaluating the use of transvaginal compared to transabdominal cerclage.
Bacterial vaginosis (BV) Bacterial vaginosis (BV) is a vaginal infection caused by an imbalance in the polymicrobial vaginal flora. It is not fully understood as to what causes this increase in commensal organisms. BV is more commonly associated with mid-trimester losses than first trimester losses. In women found to have BV in early pregnancy, a five-fold increase in mid-trimester losses has been demonstrated. There is also a substantial body of evidence implicating BV with an increased risk of pre-term delivery and associated poor perinatal outcome. Trials involving different antibiotics have thus far
F. Dawood et al.
Table 3 Predicted probability of a future successful pregnancy in women with a history of idiopathic miscarriages (95% CI). Age (years) Number of previous miscarriages
20 25 30 35 40 45
2
3
4
5
92 89 84 77 69 60
90 86 80 73 64 54
88 82 76 68 58 48
85 79 71 62 52 42
yielded conflicting results. Properly designed, randomised controlled trials are required before any treatment regime is routinely adopted. It should be borne in mind that as in the case with first-trimester losses, the aetiology of mid-trimester losses is heterogeneous. The presence of dual pathology, such as cervical weakness and bacterial vaginosis or antiphospholipid syndrome, may occur in around 10% of mid-trimester losses.
Idiopathic losses This group represents the largest diagnostic category, accounting for 50% of all RM women. Maternal age and the number of previous miscarriages are the most important parameters in predicting future success. A large prospective study of women with idiopathic RM tabulated fetal survival rates, enabling the future reproductive potential of women with idiopathic RM to be calculated using statistical actuarial analysis (Table 3). Not only is this information extremely valuable in counselling these patients and formulating their expectations, but it is immensely reassuring that even at the age of 40 years, with a history of three previous miscarriages, there is a 64% chance of a successful outcome. Supportive therapy with regular ultrasound surveillance and reassurance, ideally in a dedicated early pregnancy clinic is currently the best management option in this group.
Conclusion The clinical situation of RM continues to baffle clinicians in some 50% of cases. However, recent technological advances and novel treatment op-
ARTICLE IN PRESS Recurrent miscarriage
tions proffer a ray of optimism and augur well for the management of RM in the future.
Practice points *
*
*
*
*
Stratification of pregnancy loss affords a more structured approach to management of RM. Cytogenetic analysis of miscarried tissue should be conducted for RM women wherever the facilities exist. Endometrial sampling of tissue should be undertaken exclusively in a research setting. A proven diagnosis of antiphospholipid syndrome should be treated with low-dose aspirin. TAC is an invasive procedure and should be reserved exclusively for selected patients.
Research directions *
*
Genetic polymorphisms in acquired thrombophilia. Probing for chromosomal aberrations using FISH.
253
Further reading Farquharson RG, Quenby S, Greaves M. Antiphospholipid syndrome in pregnancy: a randomised controlled trial of treatment. Obstet Gynecol 2002;100(3):408–13. Bates MD, Quenby S, Takakuwa K, Johnson PM, Vince GS. Aberrant cytokine production by peripheral blood mononuclear cells in recurrent miscarriage. Hum Reprod 2002; 17:2439–44. Regan L, Backos MJ, Rai R. The investigation and treatment of couples with recurrent miscarriage RCOG Guideline No. 17, May 2003. Preston FE, Rosendaal FR, Walker ID, et al. Increased fetal loss in women with heritable thrombophilia. Lancet 1996;348: 913–6. Oakeshott P, Hay P, Hay S, Steinke F, Rink E, Kerry S. Association between bacterial vaginosis or chlamydia infection and miscarriage before 16 weeks’ gestation: prospective community-based cohort study. BMJ 2002;325:1334. MRC/RCOG Working Party on Cervical Cerclage. Final report of the Medical Research Council/Royal College of Obstetricians, Gynaecologists Multicentre Randomised Trial of Cervical Cerclage. BJOG 1993;100:516–23. Stephenson MD, Awartani KA, Robinson WP. Cytogenetic analysis of miscarriages from couples with recurrent miscarriage: a case-control study. Hum Reprod 2002;17:446–51. Munne S, Magli C, Cohen J, et al. Positive outcome after preimplantation diagnosis of aneuploidy in human embryos. Hum Reprod 1999;14:2191–9. Brigham SA, Conlon C, Farquharson RG. A longitudinal study of pregnancy outcome following idiopathic recurrent miscarriage. Hum Reprod 1999;14:2868–71. Scott JR. Immunotherapy for recurrent miscarriage (Cochrane Review). In: The Cochrane Library, Issue 1. Oxford, Update Software, 2003.
www.elsevier.com/cuog
Recurrent miscarriage Feroza Dawood, Roy Farquharson*, Siobhan Quenby University Department of Obstetrics and Gynaecology, Liverpool Women’s Hospital, Crown Street, Liverpool L8 7SS, UK
KEYWORDS Embryo losses; Fetal losses; Antiphospholipod syndrome; Cytogenetics; Thrombophilia
Summary Recurrent miscarriage (RM) is a challenging clinical condition accentuated by a multi-factorial aetiology. Recent research has afforded us an in-depth understanding of the complexities of the evolving pregnancy and of the potential hazards that it may face at different developmental stages. A delineation of types of pregnancy loss provides a useful framework in the management of RM. New theories have highlighted the impact of a hostile endometrium, chromosomal aberrations, abnormal immune responses and hormonal influences on recurrent pregnancy loss. Whilst the antiphospholipid syndrome retains its importance as a significant aetiology in RM, recent attention has focused on the role of other hereditary and acquired thrombophilias. As far as mid-trimester losses are concerned, the entities of cervical weakness and bacterial vaginosis are prominent features. & 2004 Elsevier Ltd. All rights reserved.
Introduction
Diagnostic categories
Recurrent miscarriage (RM) is defined as three or more consecutive pregnancy losses prior to 24 weeks of gestation. As spontaneous miscarriage complicates 15–20% of all pregnancies, by probability alone the recurrent miscarriage rate should be in the order of 0.15 ¼ 0.3–0.4%. Rather, the actual rate is much higher at 1–2%, supporting the assumption that specific underlying pathologies exist. The definition of RM traverses a wide gestational range and since various pathophysiological processes may be inflicted in different stages of pregnancy, a fundamental tool in the management of RM is to stratify the type of pregnancy loss. A suggestion of pregnancy loss classification is set out below (Table 1).
Several previously lauded theories and associations of RM have been discredited and superseded by a modern, refined and evidence-based approach. As a consequence there has been a radical shift in the investigative algorithm of recurrent miscarriage. Recent research has questioned the value of routine screening for underlying diabetes and thyroid disease in asymptomatic patients, as the prevalence of these endocrinopathies have been found to be similar in women with RM and the general population. Routine screening for toxoplasmosis, rubella, cytomegalovirus and herpes simplex virus (TORCH) is also currently deemed unnecessary. A suggested algorithm of targeted investigations, ideally based on the type of previous pregnancy losses, is outlined below (Table 2). However, one should remain cognisant that the heterogenous nature of RM implies that there may well be a convergence of aetiologies in the clinical setting. Consequently, meticulous history taking and a practical approach is mandatory.
*Corresponding author. Tel.: þ 44-151-702-4001/4221; fax: þ 44-151-702-4137. E-mail address: [email protected] (R. Farquharson).
0957-5847/$ - see front matter & 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.curobgyn.2004.04.007
ARTICLE IN PRESS 248
Table 1
F. Dawood et al.
Pregnancy loss classification.
Type of loss
Typical gestation (weeks)
Fetal heart activity
Pre-embryo Embryo Fetal Late fetal loss Spontaneous second trimester loss
o6 6–8 8–12 12–24 12–24
Never identified Never identified Cessation of fetal heartbeat Intrauterine death Fetal heart present, but cervical dilatation or SROMn precipitates in delivery
n
SROM (spontaneous rupture of membranes).
Table 2
Diagnostic investigations in recurrent miscarriage.
Type of miscarriage
Associated conditions
Investigations
Pre-embryonic and embryonic
Karyotype abnormalities
Parental karyotypes Cytogenetic analysis of miscarried tissue FSH, LH, Day 21 progesterone, pelvic ultrasound
Endocrine: PCOS Oligomenorrhea Endometrial abnormalities Immunological
Endometrial sampling (currently strictly research based) Dilute Russell Viper Venom Time (DRVVT) for lupus anticoagulant, anticardiolipin antibodies, IgG and IgM
Fetal (early and late)
Antiphospholipid syndrome Thrombophilia
Anticardiolipin antibodies (IgG and IgM), Lupus anticoagulant (DRVVT), activated protein C resistance, protein C & S deficiency, hyperhomocysteinaemia, factor V Leiden and prothrombin gene mutations
Spontaneous midtrimester losses
Anatomical Cervical weakness Bacterial vaginosis
Pelvic ultrasound, three-dimensional ultrasound Hysteroscopy, swabs for mycoplasma, ureaplasma and chlamydia
Embryonic losses The fate of the developing embryo is challenged at the outset of both the molecular and biological phases. At the epithelial juncture, abnormality with impairment of barrier function may lead to a situation in which ‘poor quality’ embryos that are otherwise destined to fail, implant and present later as miscarriages. The majority of miscarriages are embryonic losses. An interesting and as yet unexplained aspect of embryonic loss is the fact that the majority (90%) of pregnancies with an abnormal karyotype miscarry in the first trimester, while the majority (93%) of pregnancies with a normal karyotype continue. It appears that couples conceive a number of abnormal embryos and that this is further compounded by endometrial nonselectivity, resulting in RM. These hypotheses have
spawned a novel paradigm: the innovative concept of miscarriage as a natural process of quality control, and RM as failure of this quality control. Furthermore, immunological influences and a hostile endometrium have also been implicated in contributing to embryonic loss.
Karyotype abnormalities Parental peripheral blood karyotypes Parental peripheral blood karyotype abnormalities are reported in 3–5% of couples suffering recurrent miscarriage and testing of both partners is therefore advocated. The commonest abnormalities appear to be balanced reciprocal and Robertsonian translocations. Liaison with a clinical geneticist for genetic counselling is recommended. Pre-implantation
ARTICLE IN PRESS Recurrent miscarriage
genetic diagnosis (PGD), used to investigate women with RM, demonstrates that they produce more aneuploid embryos than normal women. When PGD is employed to discard karyotypically abnormal embryos (known as aneuploidy screening) the miscarriage rate after in vitro fertilisation (IVF) is reduced. These recent advances in IVF and PGD, as well as in fluorescent in situ hybridisation (FISH), afford couples afflicted with abnormal peripheral karyotypes a measured but conceivable form of treatment.
Cytogenetic analysis of miscarried tissue Culture and karyotyping of miscarried pregnancies from women suffering from RM have detected a 29–57% abnormality rate. Chorionic villous karyotyping, performed on prospective miscarriages following three or more pregnancy losses, revealed abnormality in 60% of cases. However, these figures may yet underestimate the actual incidence of chromosomal anomalies, as conventional cytogenetic analysis of miscarried tissue relies on culturing and karyotyping, a technique limited by external contamination, culture failure and selective growth of maternal cells. Analysis of spontaneous miscarriages by the technique of comparative genomic hybridisation (CGH) obviates the need for culture, thus improving detection of chromosomal imbalances. Although the routine cytogenetic analysis of miscarried products is not a widely adopted practice in most miscarriage clinics for pragmatic and financial reasons, there is strong empirical evidence that the introduction of these techniques will offer a more thorough evaluation of reproductive loss in the future.
Endometrial and immunological factors Recent research has highlighted the role of abnormal endometrial morphology in women with RM. There is emerging evidence of maladaptive changes in the endometriums of women with recurrent miscarriage. It has been hypothesised that the endometrium in women suffering from RM may be more receptive to implantation than in normal controls. This is thought to be mediated by compromised epithelial function. The expression of MUC1, an anti-adhesion molecule, has been found to be lower in the endometriums of women suffering from RM than in controls, and in vitro experiments have revealed that MUC1 is selectively removed from the human maternal epithelial cell
249
surface in the immediate vicinity of an attaching embryo. The maternal decidua is predominantly colonised by the uterine natural killer (NK) cell, also known as the uterine large granular lymphocyte (LGL). Increased numbers of CD56 þ LGL have been found in the pre-implantation endometriums of RM patients compared to controls. Furthermore, increased numbers of CD56 þ LGL leucocytes were found in the endometriums of patients who subsequently miscarried than in those who had live births. These observations have triggered two competing hypotheses: either CD56 þ LGL are hostile to invading trophoblast or CD56 þ LGL may facilitate the implantation of abnormal blastocysts, leading to the clinical presentation of RM. The latter interpretation is supported by recent data showing CD56 þ LGL are more numerous in the decidua of chromosomally abnormal miscarriages than in chromosomally normal miscarriages. Differences were detected in the decidua leucocytes from the miscarriages of women with unexplained RM and a normal fetal karyotype, when compared to that from women with RM and abnormal fetal karyotype. Cytokine aberrations The systemic maternal immune responses are governed by activated lymphocytes and macrophages which produce pleiotropic soluble proteins known as cytokines. During normal pregnancy immune responses may be biased in favour of a type 2 cytokine profile, and it has been suggested that RM is an abnormal type 1 response. A prospective study of the type 1/type 2 cytokine shift in early pregnancies of women suffering from RM revealed that the cytokine shift, which appears to characterise normal pregnancy, was accentuated rather than diminished in RM pregnant women. Therefore, in a RM population women may be immunologically more receptive to abnormal pregnancies. Immunomodulation There is no benefit derived from routine testing for HLA types or anti-paternal cytotoxic antibodies in an RM population. A recent systematic review analysed 19 randomised controlled trials of immunotherapy for recurrent miscarriage. The review deduced that neither paternal cell immunisation nor third party donor leukocytes provided any significant beneficial effects over placebo in preventing further miscarriage. The analysis also concluded that there was no improvement in subsequent live birth rates with the usage of
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trophoblast membranes and intravenous immunoglobulin compared to placebo.
Hormonal factors Although polycystic ovary syndrome (PCOS) has been reported as having a higher prevalence in RM women compared to the general population, PCOS is no longer accepted as having a significant role in the pathophysiology of RM. Another contentious issue is the belief that the treatment of lutealphase defects (progesterone deficiency induced by a malfunctioning corpus luteum) prevents pregnancy loss. There is certainly no robust evidence to justify the use of exogenous progesterone to support a pregnancy in RM patients. There is a strand of evidence supporting a causal relationship between hyperprolactinaemia and RM. However, this association requires further elucidation before any treatment options are endorsed. Oligomenorrhea The entity of oligomenorrhoea is over represented in the RM population (10–15%), in contrast to 1% in the general population. Women with oligomenorrhoea have been shown to have lower luteal phase oestradiol levels, which may alter endometrial receptivity with subsequent compromised implantation and resultant embryonic losses. The presence of oligomenorrhoea has also been shown to give a higher chance of a normal karyotype miscarriage. Although the precise role of endogenous human chorionic gonadotrophin (HCG) is not yet established, it is known that it is essential in the establishment of pregnancy. A systematic review of four trials concluded that there was insufficient evidence to evaluate the use of HCG during pregnancy to prevent miscarriage in women with a history of RM. However, there may be a case for treatment with HCG in reducing the risk of miscarriage for women with oligomenorrhoea. This needs to be expounded by randomised controlled trials.
Fetal losses Antiphospholipid syndrome (APS) The antiphospholipid syndrome (APS) remains entrenched as one of the most important causes of fetal loss. It is characterised by a clinical history of recurrent miscarriage, thrombosis or thrombocytopenia, accompanied by persistently positive tests for antiphospholipid antibodies. Tests for antiphospholipid antibodies are usually a medium to high
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titre of antibody to cardiolipin (ACA) and/or abnormalities of coagulation-based assays that are consistent with the presence of a lupus anticoagulant and should be positive on two occasions at least 6 weeks apart. The clinical obstetric criteria to diagnose APS are *
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three or more consecutive spontaneous losses before the tenth week of gestation; one or more premature births before 34 weeks due to severe pre-eclampsia or impaired fetal growth; one or more unexplained intrauterine deaths beyond 10 weeks gestation.
Thrombosis is frequently observed in the decidua and placentae of patients with APS. Indeed the underlying pathogenetic mechanism linking APS to pregnancy loss has been attributed to placental thrombosis and infarction. However, thrombosis is neither a universal nor a distinct feature of APS pregnancies. Therefore, the pathophysiological mechanisms have been extrapolated to encompass the direct effect of anticardiolipin antibodies on trophoblast invasion. Anticardiolipin antibodies have been found to directly react with trophoblast cells, preventing trophoblast proliferation. It has been discovered that ACA inhibited chemotaxis and differentiation of villous trophoblast isolated from third trimester placentae and that low-molecular weight heparin reduced the binding of ACA to trophoblast cells and restored trophoblast function. However, the clinical spectrum of disorders that are associated with ACA are more likely to be caused by placentation problems that occur in the first and second trimester than in the third trimester. ACA are associated with first and second trimester miscarriages, pre-eclampsia and intrauterine growth restriction. In pre-eclampsia and intrauterine growth restriction there are abnormalities in extravillous trophoblast (EVT) invasion. EVTs produce physiological changes in both the decidual and myometrial segments of the spiral arteries in normal pregnancy. EVT cells are a highly migratory and proliferative cell population and start to invade the decidual segments in the first trimester and the myometrial segments after 16 weeks gestation, resulting in a high flow, low impedance system. In the presence of ACA, EVT migration and invasion appears to be largely restricted to the decidual portion. The mechanisms underlying this deficient trophoblast invasion are unclear. EVTs are morphologically different from villous trophoblasts and they differ in their expression of oncogenes and adhesion molecules. Thus, the EVTs and the villous
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trophoblasts are likely to behave differently in in vitro models of trophoblast function. Apoptosis (programmed cell death) may be important in controlling trophoblast invasion and is involved in trophoblast cell turnover. Observations of increased placental apoptosis with advancing gestational age suggest that apoptosis is a normal placental process. Changes in the phospholipid component of the cell membrane are an integral, initial component of apoptosis. During the early stages of apoptosis, phosphatidylserine flips from the inner surface to the outer surface of the membrane. It is important to establish whether any interaction of ACA with the cell membrane alters apoptosis. The optimum treatment of RM women with APS is a subject of contention. While a combination of low-dose aspirin and heparin has been advocated by some authorities, the most recent randomised controlled trial of 98 women, representing the largest recruitment population to date, has clearly depicted no significant difference in the live birth rate of the study arm treated with low-dose aspirin alone, compared to the arm receiving a combination of low-dose aspirin and low-molecular weight heparin (72 and 78%, respectively). Hence, the routine use of heparin has come under scrutiny. While the heparin debate continues, treatment with aspirin 75 mg daily throughout pregnancy is definitely recommended in RM women with APS.
Thrombophilia Thrombophilic disorders have generated considerable interest in the field of RM. Thrombophilia is heralded by a predisposition to thrombosis due to a procoagulant state. Several blood clotting disorders are grouped under the umbrella term of thrombophilia. Amongst these, are activated protein C resistance (APCR), protein S deficiency, protein C deficiency, prothrombin mutation, antithrombin III deficiency and hyperhomocysteinaemia (methylenetetrahydrofolate reductase mutation, C677 T MTHFR). Clinical studies suggest that the underlying pathophysiological mechanism is mediated via hypercoagulation, leading to uteroplacental insufficiency with resultant pregnancy loss. The antiphospholipid syndrome, described previously, is an acquired thrombophilia with a wellestablished role in the aetiology of RM. More recently attention has focused on the significance of other genetic and acquired thrombophilias as potential putative factors in RM. Prothrombin gene mutation is signalled by a defect in clotting factor II at position G20210A. The relative
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risk for thrombosis in patients with this mutation is two-fold in heterozygotes. Individuals with hyperhomocysteinaemia exhibit a deficiency of folate due to the presence of the methylene tetrahydrofolate reductase mutation (MTHFR C677 T). The thrombotic risk is increased two-fold in homozygosity; and in the heterozygous state for Antithrombin III deficiency, the risk is 20- to 50-fold. APCR has emerged as the commonest genetic cause of thrombo-embolism. APCR is caused by a point mutation (Factor V Leiden, FVL) in 95% of cases. Some individuals exhibit activated protein C resistance, but do not possess this mutation. This phenomenon has been termed acquired APCR; the true aetiology of which remains an enigma. The risk of thrombosis is increased 5- to 10-fold in heterozygous carriers of FVL, and 100-fold in homozygosity. Hereditary and acquired APCR have been demonstrated by several studies to be a significant risk factor for fetal loss. An increased risk of fetal loss in women with thrombophilia compared with controls was described by a European multicentre retrospective study, incorporating all known thrombophilias. The risk of stillbirth was higher in women with multiple thrombophilic defects, suggesting a synergistic effect. While some researchers would contest screening for thrombophilia in the initial evaluation of RM, the authors opine that unexplained recurrent fetal losses should prompt testing. A personal or substantial family history of thrombosis also warrants testing. It has been suggested that anticoagulation therapy significantly improves pregnancy outcome in women with thrombophilia. This is an avenue that begs further evaluation.
Mid-trimester losses Mid-trimester losses refer to miscarriages that occur between 12 and 24 weeks of gestation and constitute approximately 5% of all pregnancy losses. The presence of dual pathology occurs in 10–15% of mid-trimester losses.
Late fetal losses Antiphospholipid syndrome is one of the most important causes of late fetal losses, but testing for other thrombophilias is also warranted.
Spontaneous mid-trimester losses Anatomical The incidence of uterine anomaly is less than 5% in RM women. Although traditionally associated with
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mid-trimester losses, uterine abnormalities may also be implicated in first trimester losses. The use of non-invasive three-dimensional ultrasound scan is gaining vogue as it provides both diagnosis and classification of uterine malformation, rendering hysteroscopy unnecessary. Cervical weakness accounts for approximately 10% of mid-trimester losses. It may follow previous damage caused by cone biopsy, operative dilatation of the cervix, or may rarely be due to a congenital defect, presenting classically as painless dilatation of the cervix, which may then lead to spontaneous rupture of membranes. Following this specific history, a pre-conceptual confirmatory hysteroscopy is recommended to assess cervical resistance and length. These findings will dictate treatment options. In cases of confirmed cervical weakness, cervical cerclage is recommended. A randomised trial of cervical cerclage was conducted by the Royal College of Obstetricians. This trial reported a marginal reduction in the number of deliveries prior to 33 weeks in the cerclage group. The current recommendation is the use of transvaginal cerclage in high-risk women, for example those with a history of three or more mid-trimester losses. In a small number of clinical cases, women experience intractable mid-trimester losses refractory to transvaginal cerclage. It is in this select group of women that transabdominal cerclage is the only remaining hope of a successful outcome. Patient selection is crucial as this intervention is not without associated complications such as iatrogenic miscarriage, uterine rupture and rarely, hysterectomy. Transabdominal suture insertion is usually undertaken at 10 weeks of gestation and subsequent delivery by elective Caesarean section is mandatory. What is certainly warranted is a randomised controlled trial with two arms evaluating the use of transvaginal compared to transabdominal cerclage.
Bacterial vaginosis (BV) Bacterial vaginosis (BV) is a vaginal infection caused by an imbalance in the polymicrobial vaginal flora. It is not fully understood as to what causes this increase in commensal organisms. BV is more commonly associated with mid-trimester losses than first trimester losses. In women found to have BV in early pregnancy, a five-fold increase in mid-trimester losses has been demonstrated. There is also a substantial body of evidence implicating BV with an increased risk of pre-term delivery and associated poor perinatal outcome. Trials involving different antibiotics have thus far
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Table 3 Predicted probability of a future successful pregnancy in women with a history of idiopathic miscarriages (95% CI). Age (years) Number of previous miscarriages
20 25 30 35 40 45
2
3
4
5
92 89 84 77 69 60
90 86 80 73 64 54
88 82 76 68 58 48
85 79 71 62 52 42
yielded conflicting results. Properly designed, randomised controlled trials are required before any treatment regime is routinely adopted. It should be borne in mind that as in the case with first-trimester losses, the aetiology of mid-trimester losses is heterogeneous. The presence of dual pathology, such as cervical weakness and bacterial vaginosis or antiphospholipid syndrome, may occur in around 10% of mid-trimester losses.
Idiopathic losses This group represents the largest diagnostic category, accounting for 50% of all RM women. Maternal age and the number of previous miscarriages are the most important parameters in predicting future success. A large prospective study of women with idiopathic RM tabulated fetal survival rates, enabling the future reproductive potential of women with idiopathic RM to be calculated using statistical actuarial analysis (Table 3). Not only is this information extremely valuable in counselling these patients and formulating their expectations, but it is immensely reassuring that even at the age of 40 years, with a history of three previous miscarriages, there is a 64% chance of a successful outcome. Supportive therapy with regular ultrasound surveillance and reassurance, ideally in a dedicated early pregnancy clinic is currently the best management option in this group.
Conclusion The clinical situation of RM continues to baffle clinicians in some 50% of cases. However, recent technological advances and novel treatment op-
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tions proffer a ray of optimism and augur well for the management of RM in the future.
Practice points *
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Stratification of pregnancy loss affords a more structured approach to management of RM. Cytogenetic analysis of miscarried tissue should be conducted for RM women wherever the facilities exist. Endometrial sampling of tissue should be undertaken exclusively in a research setting. A proven diagnosis of antiphospholipid syndrome should be treated with low-dose aspirin. TAC is an invasive procedure and should be reserved exclusively for selected patients.
Research directions *
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Genetic polymorphisms in acquired thrombophilia. Probing for chromosomal aberrations using FISH.
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Further reading Farquharson RG, Quenby S, Greaves M. Antiphospholipid syndrome in pregnancy: a randomised controlled trial of treatment. Obstet Gynecol 2002;100(3):408–13. Bates MD, Quenby S, Takakuwa K, Johnson PM, Vince GS. Aberrant cytokine production by peripheral blood mononuclear cells in recurrent miscarriage. Hum Reprod 2002; 17:2439–44. Regan L, Backos MJ, Rai R. The investigation and treatment of couples with recurrent miscarriage RCOG Guideline No. 17, May 2003. Preston FE, Rosendaal FR, Walker ID, et al. Increased fetal loss in women with heritable thrombophilia. Lancet 1996;348: 913–6. Oakeshott P, Hay P, Hay S, Steinke F, Rink E, Kerry S. Association between bacterial vaginosis or chlamydia infection and miscarriage before 16 weeks’ gestation: prospective community-based cohort study. BMJ 2002;325:1334. MRC/RCOG Working Party on Cervical Cerclage. Final report of the Medical Research Council/Royal College of Obstetricians, Gynaecologists Multicentre Randomised Trial of Cervical Cerclage. BJOG 1993;100:516–23. Stephenson MD, Awartani KA, Robinson WP. Cytogenetic analysis of miscarriages from couples with recurrent miscarriage: a case-control study. Hum Reprod 2002;17:446–51. Munne S, Magli C, Cohen J, et al. Positive outcome after preimplantation diagnosis of aneuploidy in human embryos. Hum Reprod 1999;14:2191–9. Brigham SA, Conlon C, Farquharson RG. A longitudinal study of pregnancy outcome following idiopathic recurrent miscarriage. Hum Reprod 1999;14:2868–71. Scott JR. Immunotherapy for recurrent miscarriage (Cochrane Review). In: The Cochrane Library, Issue 1. Oxford, Update Software, 2003.