Low-molecular-weight heparin for prevention of placenta-mediated pregnancy complications: protocol for a systematic review and individual patient data meta-analysis (AFFIRM)

Hypertensive Disorders of Pregnancy and Pre-Pregnancy Hypertension with Subsequent Incident Venous Thromboembolic Events

Hypertensive disorders of pregnancy (HDP) and pre-pregnancy hypertension contribute to maternal morbidity and mortality. We examined the association of HDP and pre-pregnancy hypertension with subsequent venous thromboembolic (VTE) events. The retrospective cohort study included 444,859 women with ≥1 live, singleton birth in South Carolina (2004-2016). Hospital and emergency department visit and death certificate data defined incident VTE, HDP, and pre-pregnancy hypertension. Birth certificate data also defined the exposures. Adjusted Cox proportional hazards methods modeled VTE events risk. Of the cohort, 2.6% of women had pre-pregnancy hypertension, 5.8% had HDP, 2.8% had both pre-pregnancy hypertension and HDP (both conditions), and 88.8% had neither condition. The risk of incident VTE events within one year of delivery was higher in women with HDP (hazard ratio [HR] = 1.62, 95% confidence interval [CI]: 1.15-2.29) and both conditions (HR = 2.32, 95% CI: 1.60-3.35) compared to those with neither condition as was the risk within five years for women with HDP (HR = 1.35, 95% CI: 1.13-1.60) and for women with both conditions (HR = 1.82, 95% CI: 1.50-2.20). One- and five-year risks did not differ in women with pre-pregnancy hypertension compared to women with neither condition. Compared to non-Hispanic White (NHW) women with neither condition, the incident VTE event risk was elevated within five years of delivery for NHW (HR = 1.29, 95% CI: 1.02-1.63; HR = 1.59, 95% CI: 1.16-2.17) and non-Hispanic Black (NHB; HR = 1.51, 95% CI: 1.16-2.96; HR = 2.08, 95% CI: 1.62-2.66) women with HDP and with both conditions, respectively, and for NHB women with pre-pregnancy hypertension (HR = 1.50, 95% CI: 1.09-2.07). VTE event risk was highest in women with HDP, and the event rates were higher in NHB women than in NHW women in the same exposure group.

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.

Enoxaparin Increases D6 Receptor Expression and Restores Cytoskeleton Organization in Trophoblast Cells from Preeclampsia

D6 is a scavenger receptor for CC chemokines expressed in the human placenta. It prevents excessive leukocyte tissue infiltration by internalizing chemokines through cytoskeleton-dependent intracellular transport. In preeclampsia (PE), the D6 receptor is overexpressed in trophoblast cells, but functionally impaired, due to cytoskeleton destructuring. Low molecular weight heparin (LMWH) represents a potential treatment for PE based on its anti-thrombotic and anti-inflammatory properties. Here, we investigated the effect of enoxaparin on D6 expression, and cytoskeleton organization primary cytotrophoblast cell cultures were obtained from the placentae of women with PE (n = 9) or uncomplicated pregnancy (n = 9). We demonstrated that enoxaparin is able to (i) increase D6 expression, and (ii) improve cytoskeletal fiber alignment in trophoblast cells from PE patients.

Managing antiphospholipid syndrome in pregnancy

Antiphospholipid syndrome (APS) is an autoimmune disease characterised by the presence of antiphospholipid antibodies (aPL). The antibodies currently included in the classification criteria include lupus anticoagulant (LA), anticardiolipin antibodies (aCL) and anti-^2-glycoprotein 1 antibodies (^2GPI). APS can present with a variety of clinical phenotypes, including thrombosis in the veins, arteries and microvasculature and obstetrical complications. Pregnancy complications in obstetric APS (OAPS) include unexplained recurrent early pregnancy loss, fetal death, or premature birth due to severe preeclampsia, eclampsia, intrauterine growth restriction or other consequences of placental insufficiency. Careful, well monitored obstetric care with the use of aspirin and heparin has likely improved the pregnancy outcome in obstetric APS and currently approximately 70-80% of pregnant women with APS have a successful pregnancy outcome. However, the current standard of care does not prevent all pregnancy complications as the current treatment fails in 20-30% of APS pregnancies. Other treatments options are currently being explored and retrospective studies suggest that trials with hydroxychloroquine and possibly pravastatin are warranted in pregnant women with aPL. In this review will focus on the current treatment of OAPS.

The risk of cesarean delivery after labor induction among women with prior pregnancy complications: a subgroup analysis of the AFFIRM study

Background

To determine the risk of cesarean delivery after labor induction among patients with prior placenta-mediated pregnancy complications (pre-eclampsia, late pregnancy loss, placental abruption or intrauterine growth restriction).

Methods

The AFFIRM database includes patient level data from 9 randomized controlled trials that evaluated the role of LMWH versus no LMWH during pregnancy to prevent recurrent placenta-mediated pregnancy complications. The primary outcome of this sub-study was the proportion of women who had an unplanned cesarean delivery after induction of labor compared to after spontaneous labor.

Results

There were 512 patients from 7 randomized trials included in our sub-study. There was no difference in the risk of cesarean delivery between women with labor induction (21/148, 14.2%) and spontaneous labor (79/364, 21.7%) (odds ratio (OR) 0.60, 95% CI, 0.35–1.01; p = 0.052). Among 274 women who used LMWH prophylaxis during pregnancy, the risk of cesarean delivery was lower among those that underwent labor induction (9.8%) compared to spontaneous labor (22.4%) (OR 0.38, 95% CI, 0.17–0.84; p = 0.01).

Conclusions

The risk of cesarean delivery is not increased after labor induction among a higher risk patient population with prior pregnancy complications. Our results suggest that women who receive LMWH during pregnancy might benefit from labor induction.

Current insights in obstetric antiphospholipid syndrome

PURPOSE OF REVIEW

Antiphospholipid syndrome (APS) is defined as the association of thrombotic events and/or obstetric morbidity in patients persistently positive for antiphospholipid antibodies (aPL). In this review, we will highlight the most important clinical presentations of APS with a focus on the obstetric morbidity, the current management strategies and the outlook for the future.

RECENT FINDINGS

The use of aspirin and heparin has improved the pregnancy outcome in obstetric APS and approximately 70% of pregnant women with APS have a successful pregnancy outcome. Unfortunately, the current standard of care does not prevent all pregnancy complications as the current treatment fails in 20-30% of APS pregnancies. This therefore highlights the need for alternative treatments to improve obstetrical outcome. Other treatment options are currently explored and retrospective studies show that pravastatin for example is beneficial in women with aPL-related early preeclampsia. Moreover, the immunmodulator hydroxychloroquine may play a beneficial role in the prevention of aPL-related pregnancy complications.

SUMMARY

APS is among the most frequent acquired risk factors for a treatable cause of recurrent pregnancy loss and increases the risk of conditions associated with ischaemic placental dysfunction, such as fetal growth restriction, preeclampsia, premature birth and intrauterine death. Current treatment is mainly based on aspirin and heparin. Studies to inform on alternative treatment options are urgently needed.

Antiangiogenic effects of decorin restored by unfractionated, low molecular weight, and nonanticoagulant heparins

Pregnancies affected by preeclampsia (PE) or fetal growth restriction (FGR) display increases in thrombin generation and reductions in angiogenesis and cell growth. There is significant interest in the potential for low molecular weight heparins (LMWHs) to reduce the recurrence of PE and FGR. However, LMWH is associated with an increased risk of bleeding. Therefore, it is of vital importance to determine the exact molecular function of heparins in pregnancy if they are used as therapy for pregnant women. We aimed to determine this using our model for PE/FGR in microvascular endothelial cells. The expression of decorin, a proteoglycan, was reduced to mimic PE/FGR in these cells compared with controls. Four concentrations of unfractionated heparin (UFH), LMWH, and nonanticoagulant heparin (NAC) were added to determine the effect on thrombin generation, angiogenesis, and cell growth. Treatment with UFH and LMWH reduced thrombin generation and restored angiogenesis but decreased cell growth. Treatment with NAC did not affect thrombin generation, restored angiogenesis, and showed a trend toward cell growth. In conclusion, treatment with NAC produced the same, if not better, results as treatment with UFH or LMWH, without the same impact on coagulation. Therefore, NAC could potentially be a better therapeutic option for prevention of PE/FGR in high-risk women, without the risk of the adverse effects of traditional anticoagulants.

Anticoagulants to prevent recurrent placenta-mediated pregnancy complications: Is it time to put the needles away?

Placenta-mediated pregnancy complications, such as pre-eclampsia, placental abruption, birth of a small-for-gestational age infant and late pregnancy loss, are common and carry significant morbidity and mortality. The etiology of placenta-mediated pregnancy complications is likely multifactorial and may include abnormal coagulation activation of the maternal-fetal interface. The use of antepartum low-molecular-weight heparin (LMWH) prophylaxis to prevent recurrent placenta-mediated pregnancy complications has become common practice despite limited and conflicting evidence to support its use. This paper reviews the evidence, including recently published data from an individual patient level meta-analysis, which challenges the role of LMWH in preventing recurrent placenta-mediated pregnancy complications. Incorporating this recent evidence, we recommend against the use of LMWH to prevent recurrent placenta-mediated pregnancy complications in women with and without inherited thrombophilia.

Inherited thrombophilia: a double-edged sword

Inherited thrombophilia is a blood coagulation disorder that increases the risk for venous thromboembolism (VTE). During the last decades, the practice of testing has evolved from testing selected populations, leading to high perceived risks, to broad testing for various conditions that included VTE, arterial thrombosis, and pregnancy complications. Because results of such tests usually do not guide treatment decisions, not testing patients with VTE for inherited thrombophilia is on the "Choosing Wisely" list endorsed by multiple specialty societies, including ASH. Inherited thrombophilia can be regarded a double-edged sword, as despite the rationale not to test, it is still being performed frequently. Another way of seeing inherited thrombophilia as a double-edged sword lies in its 2-sided association with reproduction, both in men and in women. Current areas of research are whether women with inherited thrombophilia and pregnancy complications benefit from anticoagulant therapy with regard to improving the chance of a successful pregnancy. Potential effects of inherited thrombophilia, most notably factor V Leiden, on improved embryo implantation in women and sperm counts in men are intriguing, but are currently poorly understood.

Low-molecular-weight heparin and recurrent placenta-mediated pregnancy complications: a meta-analysis of individual patient data from randomised controlled trials

BACKGROUND

Placenta-mediated pregnancy complications include pre-eclampsia, late pregnancy loss, placental abruption, and birth of a small-for-gestational-age (SGA) neonate. These complications are leading causes of maternal, fetal, and neonatal morbidity and mortality in high-income countries. Affected women are at high risk of recurrence in subsequent pregnancies; however, effective strategies to prevent recurrence are absent. Findings from our previous study-level meta-analysis suggested that low-molecular-weight heparin reduced the risk of recurrent placenta-mediated pregnancy complications. However, we identified significant heterogeneity in the results, possibly due to trial design or inclusion criteria. To identify which patients benefit from, and which outcomes are prevented by, low-molecular-weight heparin, we did an individual patient data meta-analysis.

METHODS

We did a systematic review in May, 2013, which identified eight eligible randomised trials done between 2000 and 2013 of low-molecular-weight heparin to prevent recurrent placenta-mediated pregnancy complications. We excluded studies on the basis of the wrong population, the study being ongoing, inability to confirm eligibility of participants, intervention stopped too early, and no response from the principal investigator. We requested individual patient data from the study authors for eligible women (women pregnant at the time of the study with a history of previous pregnancy that had been complicated by one or more of the following: pre-eclampsia, placental abruption, birth of an SGA neonate [<10th percentile], pregnancy loss after 16 weeks' gestation, or two losses after 12 weeks' gestation) and recoded, combined, and analysed the data for our meta-analysis. The primary outcome was a composite of early-onset (<34 weeks) or severe pre-eclampsia, birth of an SGA neonate (<5th percentile), late pregnancy loss (≥20 weeks' gestation), or placental abruption leading to delivery, assessed on an intention-to-treat basis. We assessed risk of bias with the Cochrane Risk of Bias tool. This study is registered with PROSPERO, number CRD42013006249.

FINDINGS

We analysed data from 963 eligible women in eight trials: 480 randomly assigned to low-molecular-weight heparin and 483 randomly assigned to no low-molecular-weight heparin. Overall, the risk of bias was not substantial enough to affect decisions regarding trial inclusion. Participants were mostly white (795/905; 88%) with a mean age of 30·9 years (SD 5·0) and 403/963 (42%) had thrombophilia. In the primary analysis, low-molecular-weight heparin did not significantly reduce the risk of recurrent placenta-mediated pregnancy complications (low-molecular-weight heparin 62/444 [14%] versus no low-molecular-weight heparin 95/443 (22%) absolute difference -8%, 95% CI -17·3 to 1·4, p=0·09; relative risk 0·64, 95% CI 0·36-1·11, p=0·11). We noted significant heterogeneity between single-centre and multicentre trials. In subgroup analyses, low-molecular-weight heparin in multicentre trials reduced the primary outcome in women with previous abruption (p=0·006) but not in any of the other subgroups of previous complications.

INTERPRETATION

Low-molecular-weight heparin does not seem to reduce the risk of recurrent placenta-mediated pregnancy complications in at-risk women. However, some decreases in event rates might have been too small for the power of our study to explore.

FUNDING

Canadian Institutes of Health Research.

[Can we prevent preeclampsia?]

Preeclampsia (PE), a specific complication of pregnancy, is one of the most frequent causes of maternal and fetal morbidity and mortality in the world. Recently, PE risk calculation algorithms allowing early detection of PE in the first trimester of pregnancy have been described. The aim of early detection would be to rapidly introduce an effective preventive treatment. The aim of our work is to study the different preventive treatments through the literature. Aspirin has some efficiency and reduces the risk of PE from 10 to 24%. It is most effective when the dose exceeds 75mg and when introduced before 16 gestational age. Early introduction of aspirin mainly prevents severe and preterm PE. Low molecular weight heparin (LMWH) and vitamin D appear to be promising therapy for PE but further research is required. Calcium administered at 1g/day reduces the risk of PE especially to patients with low baseline calcium intake. A low dose of calcium could also reduce the risk of PE but this must be confirmed. Other preventive measures (antioxidants, nitric oxide, progesterone, rest, exercise) do not reduce the incidence of PE.

Complement Split Products in Amniotic Fluid in Pregnancies Subsequently Developing Early-Onset Preeclampsia

Objective. To determine the second-trimester amniotic fluid concentrations of complement split products in pregnancies subsequently affected by early-onset preeclampsia. Study Design. Cohort of 731 women with singleton pregnancies undergoing second-trimester genetic amniocentesis followed up to delivery and analyzed as a nested case-control study. Cases of preeclampsia developing before 34 weeks' gestation (n = 15) were compared with 47 uncomplicated term controls. Amniotic fluid collected at amniocentesis was tested for complement split products Bb, C4a, C3a, and C5a. Results. Women who developed early-onset preeclampsia as compared with the term pregnant controls had significantly higher (P = 0.04) median amniotic fluid C3a levels (318.7 ng/mL versus 254.5 ng/mL). Median amniotic fluid Bb levels were also significantly higher (P = 0.03) in preeclamptic women than in normal pregnant women (1127 ng/mL versus 749 ng/mL). Median levels of C4a and C5a were not significantly different between the groups. Conclusion. Our data suggest that complement activation in early pregnancy is associated with early-onset preeclampsia. We believe this to be the first prospective study to link complement activation in amniotic fluid in early pregnancy and later development of preeclampsia. Our findings provide evidence that immune dysregulation may precede the clinical manifestations of preeclampsia and that the alternative complement pathway is principally involved.

New studies of low-molecular-weight heparin in pregnancy

Several aspects of the diagnostic and therapeutic management of women with venous thrombosis are uncertain, because of the absence of adequately sized observational or intervention studies. Here, I will discuss the rationale and design of two currently ongoing investigator-initiated, international, randomized controlled trials of LMWHin pregnancy. The Highlow study (www.highlowstudy.org; NCT Clinicaltrials.gov) 01828697) investigates two doses of low-molecular-weight heparin to prevent recurrent venous thromboembolism (VTE) in pregnant women with a history of VTE. The ALIFE2 study (www.alife2study.org; www.trialregister.nl, NTR 3361) investigates the effect of LMWH on live birth in women with inherited thrombophilia and two or more miscarriages.