Antithrombotic treatment for pregnancy complications: which path for the journey to precision medicine?

Use of anticoagulants to improve pregnancy outcomes in couples positive for M2 haplotype: A systematic review

BACKGROUND

Placental mediated pregnancy complications (PMPC) are common, often recurring, and pose a significant health risk to mother and fetus. Evidence suggests that the hypercoagulable state associated with many PMPC, could reflect reduced expression of Annexin 5 (ANXA5), a naturally occurring anticoagulant protein in placental tissue. The ANXA5 M2 haplotype is a genetic variant, which results in reduced expression of ANXA5 protein. M2 haplotype carrier couples may therefore be at increased risk of PMPC. Evidence regarding the effectiveness of anticoagulation to prevent PMPC is inconsistent. Furthermore, studies have not selected or stratified for M2 haplotype carriers, in whom there is a predisposition to hypercoagulability, to assess the effectiveness of anticoagulation, which may vary from those without the M2 haplotype.

OBJECTIVES AND RATIONALE

The aim of this study was to systematically review the current evidence to assess whether anticoagulant treatment improves pregnancy outcomes in couples positive for M2 haplotype.

SEARCH METHODS

The review was registered on PROSPERO (CRD42022343943). A comprehensive literature search was performed using MEDLINE, Embase and Cochrane collaboration databases from inception to January 2023. Two reviewers assessed the articles for eligibility and extracted the data simultaneously. Primary outcome was successful pregnancy and live birth. Secondary outcomes included PMPC (implantation failure, miscarriage, pre-eclampsia, preterm birth and fetal growth restriction).

OUTCOMES

From a pool of 410 references, 10 were selected for full text review, of which three studies (a post hoc analysis of a randomised controlled trial, cohort study and a case report) were included in this review. Included studies comprised of 223 individuals, 129 of whom who received anticoagulation treatment after testing positive for M2 haplotype. The studies collectively showed an improvement in pregnancy outcomes in M2 haplotype positive individuals however, given the heterogeneity of studies, it was not possible to conduct a meta-analysis and draw firm conclusions.

WIDER IMPLICATIONS

Current evidence is limited, such that the value of screening couples for the M2 haplotype to select or stratify for treatment with prophylactic anticoagulation remains unknown. Thus, further studies including well designed, large, multi-centre randomised controlled trials are required to assess whether anticoagulation treatment will be effective in improving pregnancy outcomes in M2 haplotype couples.

Assessment-based management of placenta-mediated pregnancy complications: Pragmatism until a precision medicine approach evolves

The management of pregnant women with thrombophilia and a history of gestational vascular complications remains debatable. Treatment of the latter is often based on clinical outcome rather than disease mechanism. While the use of venous thromboembolism prophylaxis in pregnancy is recommended for those at increased risk, the ability of anticoagulant and/or antiplatelet agents to lower the risk of placenta-mediated complications in this clinical setting remains controversial. The available guidelines are inconsistent in some situations, which reflects the limited evidence base. This review critically discusses risk assessment models (RAMs) and management strategies of women with thrombophilia and pregnancy complications, using clinical vignettes. RAMs, taking into account obstetric and thrombotic history as well as thrombophilia status, could drive a precision medicine approach, based on disease mechanism, and guide individual therapeutic interventions in high-risk clinical settings.

Management of heparin resistance due to antithrombin deficiency in a Chinese pregnant woman: a case report

Untreated individuals with antithrombin (AT) deficiency are at higher risk of thrombosis and adverse pregnancy outcomes. The present recommendations are mostly empirical for treating patients with AT deficiency during pregnancy because of the absence of guidelines. We report a rare case of heparin resistance due to AT deficiency in a pregnant 32-year-old Chinese woman. We also reviewed the English medical literature for AT deficiency and its association with thromboembolism and treatment. This patient suffered two early miscarriages because of thrombosis due to AT deficiency. The patient was administered the combination of adequate low molecular weight heparin with fresh frozen plasma and warfarin because of her heparin resistance. She delivered a healthy female newborn without any adverse effects of the anticoagulation therapy. Our findings suggest that the combination of adequate low molecular weight heparin with fresh frozen plasma and warfarin is effective for preventing thrombus during pregnancy.

Findings from a multicentre, observational study on reproductive outcomes in women with unexplained recurrent pregnancy loss: the OTTILIA registry

STUDY QUESTION

What evaluation and care is offered to women after unexplained recurrent pregnancy loss (RPL) or intra-uterine foetal death (IUFD) and what are the reproductive outcomes?

SUMMARY ANSWER

Women are assessed for thrombophilia and often treated with low-molecular weight heparin (LMWH) and/or low-dose aspirin (ASA).

WHAT IS KNOWN ALREADY

Randomized controlled trials (RCTs) on possible efficacy of heparins and/or aspirin have been inconclusive due to limited power to detect a difference and patient heterogeneity.

STUDY DESIGN, SIZE, DURATION

Prospective multicentre cohort study performed in 12 hospitals in three countries between 2012 and 2019.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All consecutive pregnant women with recurrent PL (≥3 losses or 2 losses in the presence of at least one euploid foetal karyotype) or at least one IUFD. Eligible women may have undergone thrombophilia testing before conception, at the discretion of local providers. The possible assignment of women to treatments (such as LMWH) was not decided a priori but was determined based on the responsible provider's current practice. Aims of the study were: (i) to evaluate factors associated with pregnancy outcome; (ii) to compare clinical management strategies in women with and without a subsequent successful pregnancy; and (iii) to evaluate characteristics of women who may benefit from antithrombotic therapy. A propensity score matching method was used to balance the differences in baseline characteristics.

MAIN RESULTS AND THE ROLE OF CHANCE

A matched sample of 265 pregnant women was analysed, with all undergoing thrombophilia screening; 103 out of 119 (86.6%) with and 98/146 (67.1%) without thrombophilia were prescribed with LMWH and/or ASA. Overall, live-births were recorded in 204 cases (77%), PL or IUFD in 61 (23%) pregnancies. Logistic regression showed a significant interaction between thrombophilia and treatment with LMWH (P = 0.03). Findings from sensitivity analysis showed odds ratio (OR) for pregnancy loss in women with inherited or acquired thrombophilia in absence of any treatment was 2.9 (95% CI, 1.4-6.1); the administration of LMWH (with or without ASA) was associated with higher odds of live-birth (OR, 10.6; 95% CI, 5.0-22.3). Furthermore, in women without thrombophilia, the odds of live-birth was significantly and independently associated with LMWH prophylaxis (alone or in association with ASA) (OR, 3.6; 95% CI, 1.7-7.9).

LIMITATIONS, REASONS FOR CAUTION

While the propensity score matching allows us to balance the differences in baseline characteristics, it does not eliminate all confounding.

WIDER IMPLICATIONS OF THE FINDINGS

Antithrombotic prophylaxis during pregnancy may be effective in women with otherwise unexplained PL or IUFD, and even more useful in those with thrombophilia.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by Italian Ministry of Health (Ricerca Corrente 2018-2020). Dr G.P. has received research grant support from Bristol Myers Squibb/Pfizer Alliance, Janssen, Boston Scientific Corporation, Bayer, and Portola and consultant fees from Amgen and Agile Therapeutics. Dr E.G. has received consultant fees from Italfarmaco and Sanofi. All other authors declare that they have no conflict of interest.

TRIAL REGISTRATION NUMBER

NCT02385461.

The endothelial protein C receptor plays an essential role in the maintenance of pregnancy

Placenta-mediated pregnancy complications are a major challenge in the management of maternal-fetal health. Maternal thrombophilia is a suspected risk factor, but the role of thrombotic processes in these complications has remained unclear. Endothelial protein C receptor (EPCR) is an anticoagulant protein highly expressed in the placenta. EPCR autoantibodies and gene variants are associated with poor pregnancy outcomes. In mice, fetal EPCR deficiency results in placental failure and in utero death. We show that inhibition of molecules involved in thrombin generation or in the activation of maternal platelets allows placental development and embryonic survival. Nonetheless, placentae exhibit venous thrombosis in uteroplacental circulation associated with neonatal death. In contrast, maternal EPCR deficiency results in clinical and histological features of placental abruption and is ameliorated with concomitant Par4 deficiency. Our findings unveil a causal link between maternal thrombophilia, uterine hemorrhage, and placental abruption and identify Par4 as a potential target of therapeutic intervention.

Neurodevelopment of high and low-risk pregnancy babies at 6 months of age

OBJECTIVE

to compare neurodevelopment differences between babies born from low-risk pregnancies and babies born from high-risk pregnancies.

STUDY DESIGN

Longitudinal design SETTING: Spain PARTICIPANTS: A total of 91 women participated in the study, divided into two groups: 49 women in the low-risk pregnancy group and 42 women in the high-risk group.

MEASUREMENT AND FINDINGS

The average amount of cortisol in pregnant mothers' hair was determined in both groups. Following their birth, the babies' neurodevelopment was evaluated using the Bayley-III instrument at 6 months of age and a new sample of cortisol was obtained from both the baby and the mother. The results showed that pregnancy risk group could predict cognitive, fine motor, gross motor and general motor neurodevelopment.

KEY CONCLUSIONS

These results seem to show that an appropriate treatment tailored to the needs of individualised pregnancies may favor babies' neurodevelopment, including that of babies born from high-risk pregnancies.

IMPLICATIONS FOR RESEARCH

It is essential to take special care of pregnant women no matter their medical condition and offer them the best medical care available.

Low molecular weight heparins use in pregnancy: a practice survey from Greece and a review of the literature

Background

Use of LMWH in pregnancy is not only limited to VTE management, but it extends, to the management of vascular gestational complications and the optimization of IVF pregnancies despite the lack of concrete scientific evidence. In this context, we conducted the present study aiming to gain insights regarding the use of LMWH during pregnancy and puerperium. We recorded indication for use, diagnostic work-up as well as the safety and efficacy of the treatment, trying to elucidate the clinical practice in our country.

Methods

We analyzed data regarding 818 pregnant women received LMWH during 2010-2015.Our cohort had a median age of 33.9 years and a BMI of 23.6.There were 4 groups: those with a history of VTE [Group-A: 76], those with pregnancy complications [Group-B: 445], those undergoing IVF [Group-C: 132] and those carrying prothrombotic tendency (thrombophilia, family history of VTE, other) [Group-D: 165]. Mean duration of LMWH administration was 8.6 ± 1.5 months. Out of the total number, 440 received LMWH in fixed prophylactic dose, 272 in higher prophylactic-weight adjusted dose and 106 in therapeutic dose. Moreover, 152 women received in addition low-dose acetylsalicylic acid (ASA). 93.8% of pregnancies were single and 6.2% were multiple ones. Live births occurred in 98.7% of pregnancies.

Results

Anticoagulation was efficacious and well tolerated. Seventeen VTE events were recorded; 7 of them antepartum and 10 postpartum. No major bleeding events were observed while 13 clinical relevant non-major bleeding events were recorded. Regarding gestational vascular complications, 28 IUGR events were recorded, as well as 48 cases of preterm labor of which 12 were concomitant with IUGR (25%). Six early pregnancy losses were recorded; there were 3 fetal deaths and 3 cases of pre-eclampsia/eclampsia.

Conclusions

LMWHs are used extensively during pregnancy and puerperium in Greece for VTE treatment and prophylaxis and for a variety of other indications as well. Although the drug has been shown to be both safe and efficacious, its use for some indications has no proven scientific evidence. In order to clearly define the role of LMWHs in pregnancy, beyond thromboprophylaxis, large prospective studies are required, which could be based on the conclusions of this study.

Thrombosis and hemostasis health in pregnancy: Registries from the International Society on Thrombosis and Haemostasis

Online patient registries are used to collect data on clinical conditions with rare occurrence or unclear diagnostic and management practices. The success of these registries depends on clear definition of goals, correct identification of patient population/inclusion criteria, availability of appropriate setup and maintenance tools, and the quality of dissemination. The Scientific and Standardization Committee (SSC) for Women's Health Issues in Thrombosis and Hemostasis, one of 20 committees of the International Society on Thrombosis and Haemostasis (ISTH) has developed 6 registries for women's bleeding and thrombotic conditions over the past 2 years and are currently in various stages of progress. Here, we provide information about these registries, including rationale, objectives, and methods for data collection. The aim is to enhance worldwide participation and thus promote the success of these registries. We used ISTH REDCap, a mature and secure Web application for building and managing online surveys and databases, and the ISTH advertising platform to maximize participation. Registries (links and project details available on ISTH and Women's SSC Web sites) include: (1) WiTEAM, project on thrombophilia and placenta-mediated obstetric complications; (2) a registry for disseminated intravascular coagulation in pregnancy; (3) severe congenital protein C deficiency-an obstetric study; (4) obstetric and gynecologic outcomes of women with platelet function disorders; (5) thrombolysis and invasive treatments for massive pregnancy-related pulmonary embolism; (6) pregnancy and exposure to direct oral anticoagulants. The ISTH promotes online registries on women's issues to enhance understanding of current practices, identify knowledge gaps, promote research, and ultimately improve patient safety and quality of life.

In vitro fertilization outcomes in women with antiphospholipid antibodies circulation

Background: Antiphospholipid antibodies (aPL) have a multifaceted effect on the hemostatic system, damaging all its protective links.Aim: To study the effect of APA on outcomes of assisted reproductive technologies (ART).Study design: We examined 267 women with infertility, who planned pregnancy using ART. They included 178 women with IVF failure (I group) and 89 women with pregnancy after the IVF program (II group). The comparison group consisted of 80 pregnant women after IVF (male factor); a control group included 80 pregnant women with physiological pregnancy. Results of study demonstrated a high frequency of aPL circulation in a group of women with IVF failures. Overall, the proportion of aPL among all 267 women who planned pregnancy with ART was 32.6%. Elevated levels of aPL in the structure of causes of IVF failures (group I) were observed in 42.1% of them. Among women whose pregnancy occurred with ART (II group) the rate of APA was 19.1%. In the comparison group, in 6.3% of cases, aPL circulation was observed. In the control group, the rate was 3.4%.Conclusion: Considering the high percentage of aPL circulation in the case of IVF failures, authors think that high titers of aPL are a temporary contraindication for IVF. Patients with a history of aPL circulation are required to receive anticoagulant therapy from the first days of the hormonal protocol. The drug of choice is a group of low molecular weight heparins (LMWH). An individual approach is extremely important with the possible identification of causes of IVF failures and selective therapy, which leads to a significant improvement in the outcomes of the IVF program.

Aspirin use during pregnancy and hypoxia-related placental pathology

OBJECTIVE

Aspirin has been shown to prevent preeclampsia. But the mechanisms remain unclear despite that improved placental circulation is considered as an underlying contributor. Our aim was to examine the hypoxia-related morphological and histopathological placental measures in relation to aspirin use during pregnancy.

STUDY DESIGN

We used the Collaborative Perinatal Project (CPP) data, which is a cohort study conducted in the U.S. from 1959 to 1976. A total of 23, 604 women who had information on placental pathology and aspirin intake during pregnancy were included in the analysis. Among them, 1474 women had a history of hypertension or preeclampsia/eclampsia and were classified as a high-risk population; the rest were considered as a low-risk population. 47 placenta measures considered to be relevant to hypoxia were selected to build a composite hypoxia- related placenta index. The generalized linear mixed model was used to fit the relationship between aspirin and placental pathology.

MAIN OUTCOME MEASURES

Hypoxia-related placental pathology.

RESULTS

Aspirin use during pregnancy was associated with a reduced risk of hypoxia-related placental pathology in the high-risk population [the adjusted odds ratio and 95% confidence interval in the 1st, 2nd, and 3rd trimesters: 0.55 (0.31, 1.00), 0.76 (0.49, 1.17), and 0.53 (0.29, 0.94), respectively]. Longer duration of aspirin use in pregnancy tended to have a lower risk of hypoxia-related placental pathologies in the high-risk population.

CONCLUSIONS

Aspirin use during pregnancy reduced risks of hypoxia-related placental pathologies in the high-risk women for preeclampsia. The duration of aspirin use determined its effects.

Aspirin Effect on Adverse Pregnancy Outcomes Associated With Stage 1 Hypertension in a High-Risk Cohort

Recently, the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines revised the recommendations for diagnosis of chronic hypertension. The new classification system includes a diagnosis of stage 1 hypertension in adults with blood pressures 130 to 139/80 to 89 mm Hg. We sought to compare outcomes among women at high risk for preeclampsia with stage 1 hypertension and assessed whether women with stage 1 hypertension had benefit from aspirin treatment compared with high-risk normotensive women. We performed a secondary analysis of the high-risk aspirin trial and included women with prior preeclampsia or diabetes mellitus. Among these women, 827 (81%) were classified as normotensive, whereas 193 (19%) were classified as stage 1 hypertensive. Among women receiving placebo, preeclampsia occurred significantly more often in women with stage 1 hypertension compared with normotensive high-risk women after adjustment for maternal age and body mass index (39.1% versus 15.1%; risk ratio, 2.49; 95% confidence interval, 1.74-3.55). Further, women with stage 1 hypertension had a significant risk reduction related to aspirin prophylaxis (risk ratio, 0.61; 95% confidence interval, 0.39-0.94) that was not seen in normotensive high-risk women (risk ratio, 0.97; 95% confidence interval, 0.70-1.34). Application of the American College of Cardiology/American Heart Association guidelines in a high-risk population demonstrates that in the setting of other risk factors, the presence of stage 1 hypertension is associated with a significantly increased risk of preeclampsia when compared with high-risk normotensive women. These findings emphasize the importance of recognition of stage 1 hypertension as an additive risk factor in women at high risk for preeclampsia and the benefit of aspirin.

LMWH in IVF - Biomarkers and benefits

There is biological plausibility that coagulation activation underlies a proportion of in vitro fertilisation IVF failures and recurrent early clinical pregnancy loss (RPL). However, low-molecular-weight heparin (LMWH) use, based upon previous clinical outcome alone, is not effective in preventing RPL. RPL is heterogeneous in mechanism. Identifying those with an underlying thrombotic mechanism would allow stratification for LMWH treatment. Annexin A5 is an anticoagulant protein expressed on the trophoblast surface. The annexin A5 M2 haplotype (ANXA5 M2) is associated with several placenta mediated pregnancy complications (PMPC) and poor IVF outcome. It is transmitted equally by males and females. A pragmatic observational study of IVF couples screened for M2 carriage and treated with LMWH achieved a 37.9% live birth rate, similar to an unscreened and untreated group with fewer adverse risk factors for conception and a better prognosis from assisted conception. This suggests that LMWH may counteract the adverse effects of M2 carriage. Using this biomarker to stratify IVF and PMPC patients for LMWH treatment merits further evaluation.

Impact of haemostatic mechanisms on pathophysiology of preeclampsia

Preeclampsia (PE) is disorder of new onset hypertension and proteinuria during the second half of pregnancy. There is increasing evidence to implicate placental over-expression of tissue factor and PAR-1 in the pathophysiology of PE. Excessive activation of platelets, neutrophils and the complement system may also contribute to the placental pathology and maternal endothelial responsible for the symptoms of PE. Increased knowledge in this field may identify new therapeutic strategies for the treatment of PE.

[For a targeted use of aspirin]

The use of low-dose aspirin in pregnancy should remain a highly targeted indication since its long-term safety has not been established and should be restricted to women at high risk of vascular complications. Indications for which the benefit of aspirin has been shown are women with a history of preeclampsia responsible for a premature birth before 34 weeks, those having at least two history of preeclampsia, those with an antiphospholipid syndrome and those with lupus associated with positive antiphospholipid antibodies or renal failure. In all other cases, the level of evidence of the benefit of aspirin is insufficient to recommend its routine prescription.

Algorithm-Driven Dosage Decisions (AD3): Optimizing Treatment for Children With Language Impairment

BACKGROUND

This study was designed to provide recommended amounts of treatment to achieve the optimal amount of language gain for children with language impairment.

METHOD

The authors retrospectively analyzed treatment outcomes for 233 children for delivered dose, intensity, and cumulative intensity of therapy. The steps of the analytical process they applied to arrive at algorithms for recommended amounts of treatment were (1) multilevel modeling to predict children's language gains from the 3 intensity parameters and (2) extraction of regression weights to create a recommended amount of treatment.

RESULTS

Optimal outcomes can be identified using an equation specifying Ŷ = desired points of change (e.g., 0.6 SD units), V = child's baseline language skills, D = average number of minutes spent targeting language in a session, F = total number of sessions conducted across the year, and D × F = product of planned dose and frequency (cumulative intensity). Input of the values for Ŷ and V provides recommended amount of treatment.

CONCLUSIONS

This study constitutes the first effort to provide empirical guidance on intensity of treatment for children with language impairment. The use of algorithm-driven dosage recommendations may be more effective than clinician judgment and trial and error, although these correlational results must be confirmed with experimental methods.

Low-molecular-weight heparin and aspirin use in relation to pregnancy outcome in women with systemic lupus erythematosus and antiphospholipid syndrome: A cohort study

OBJECTIVE

To relate anticoagulant use to pregnancy complications in women with systemic lupus erythematosus (SLE) and primary antiphospholipid syndrome (APS).

METHODS

All ongoing pregnancies, 184, in two Dutch tertiary centers between 2000 and 2015.

RESULTS

LMWH and aspirin was prescribed in 15/109 SLE women without antiphospholipid antibodies (aPL), 5/14 with aPL, 11/13 with APS, 45/48 with primary APS. Main complications in the four treatment groups (no anticoagulant treatment, aspirin, LMWH, aspirin and LMWH) included hypertensive disorders of pregnancy (9.4%, 23.3%, 50%, 18.4%, respectively, p = 0.12) and preterm birth (16.7%, 34.3%, 75%, 36.8%, respectively, p < 0.001).

CONCLUSION

Maternal and perinatal complications occurred frequently, despite LMWH and aspirin use.

Precision Medicine in Assisted Conception: A Multicenter Observational Treatment Cohort Study of the Annexin A5 M2 Haplotype as a Biomarker for Antithrombotic Treatment to Improve Pregnancy Outcome

BACKGROUND

Pregnancy failure and placenta mediated pregnancy complications affect >25% of pregnancies. Although there is biological plausibility for a procoagulant mechanism underlying some of these events, antithrombotic intervention trials demonstrate limited benefit, possibly through lack of stratification in heterogeneous patient groups. The ANXA5 M2 haplotype is a possible procoagulant biomarker and was tested pragmatically to determine whether this screening and LMWH treatment normalized the outcome for ANXA5 M2 positive couples. This was a pragmatic study that aimed to measure the effectiveness of a testing (for the M2 haplotype) and treatment (LMWH) pathway in routine clinical practice where there is variation between patients. Such a study in couples with fertility problems can inform choices between treatments; it is then the management protocol which is the subject of the investigation, not the individual treatments.

METHODS

Couples (N=77) with one or both partners ANXA5 M2 positive demonstrated association of this haplotype with adverse IVF outcome. A pragmatic, multicenter, prospective cohort study of ANXA5 M2 haplotype screening, and LWMH treatment following embryo transfer (ET) in 103 IVF couples positive for ANXA5 M2 was performed. They were compared with a group of 1000 contemporaneous randomly selected unscreened and untreated couples undergoing assisted conception, from which 103 matched control couples were derived. The primary outcome measure was live birth incidence. Secondary outcomes were results following embryo transfer (ET) and live birth outcome by gender and M2 carriage, and allelic dose influence.

FINDINGS

The tested and treated cohort of ANXA5 M2 carriers achieved a similar live birth rate (37.9%) per ET cycle compared to both the more fertile comparison group (38.5%), and to the 103 matched controls (33.0%). Significantly more treated male carrier only couples had a live birth versus female M2 only (47.7% vs. 25.0% p=0.045).

INTERPRETATION

Pragmatic ANXA5 M5 screening and treatment with LMWH in couples undergoing IVF is associated with similar outcome to couples with more favorable prognostic factors. The difference in live birth outcome for treated male only carrier couples may be consistent with an additional maternal thrombophilic factor that may adversely affect pregnancy, although other mechanisms are possible. This study suggests that LMWH treatment should be started prior to clinical pregnancy.

Management of inherited thrombophilia in pregnancy

Adverse pregnancy outcomes, such as pregnancy loss and pre-eclampsia, are associated with thrombotic mechanisms and thrombophilia. Antithrombotic interventions, particularly low-molecular-weight heparin, have been investigated in women identified by previous pregnancy outcome; however, the results have been inconsistent. This may reflect heterogeneity of both the study groups and the disease processes resulting in inadequate stratification to guide antithrombotic interventions. Furthermore, the variation in gestation at initiation of low-molecular-weight heparin treatment might be important. Despite limited evidence of efficacy, low-molecular-weight heparin is often used in an attempt to prevent these complications, owing to the lack of other effective treatments and its perceived safety in pregnancy. Research is required to better understand the disease processes, identify possible biomarkers and thereby more homogeneous groups for targeted treatment.

Thrombophilia and Pregnancy Complications

There is a paucity of strong evidence associated with adverse pregnancy outcomes and thrombophilia in pregnancy. These problems include both early (recurrent miscarriage) and late placental vascular-mediated problems (fetal loss, pre-eclampsia, placental abruption and intra-uterine growth restriction). Due to poor quality case-control and cohort study designs, there is often an increase in the relative risk of these complications associated with thrombophilia, particularly recurrent early pregnancy loss, late fetal loss and pre-eclampsia, but the absolute risk remains very small. It appears that low-molecular weight heparin has other benefits on the placental vascular system besides its anticoagulant properties. Its use is in the context of antiphospholipid syndrome and recurrent pregnancy loss and also in women with implantation failure to improve live birth rates. There is currently no role for low-molecular weight heparin to prevent late placental-mediated complications in patients with inherited thrombophilia and this may be due to small patient numbers in the studies involved in summarising the evidence. There is potential for low-molecular weight heparin to improve pregnancy outcomes in women with prior severe vascular complications of pregnancy such as early-onset intra-uterine growth restriction and pre-eclampsia but further high quality randomised controlled trials are required to answer this question.

Aspirin and heparin in pregnancy

INTRODUCTION

A pro-coagulant state during pregnancy can be involved in the occurrence of gestational vascular complications (GVCs) and venous thromboembolism (VTE).

AREAS COVERED

Antithrombotic drugs are used to prevent GVCs and VTE. Aspirin is not efficacious to prevent recurrences in women with previous early loss, while it can prevent pre-eclampsia in some groups of women. Heparins are not effective in the prevention of early recurrent loss and there is uncertainty about their efficacy in women carrying inherited thrombophilias. They could be efficacious in the prevention of GVCs in carriers of inherited thrombophilias, as GVCs have heterogeneous causes, and future studies have to focus on more homogeneous groups of patients. Not enough data are available regarding prophylaxis with heparins to prevent pregnancy-related VTE, but an accurate risk stratification of women during pregnancy and puerperium is crucial for administering prophylaxis in moderate-/high-risk women. Aspirin does not improve live births after assisted reproductive technologies, while heparins increase the number of clinical pregnancies and live births.

EXPERT OPINION

Aspirin is efficacious in the prevention of GVCs in women at risk for pre-eclampsia and in those with antiphospholipid antibodies syndrome. Heparins could give benefit to women at risk for GVCs and/or pregnancy-related VTE.