Low-Dose Aspirin for Preventing Preeclampsia and Its Complications: A Meta-Analysis

How important is aspirin adherence when evaluating effectiveness of low-dose aspirin?

Low-dose aspirin (LDA) is advocated for women at high-risk of pre-eclampsia, providing a modest, 10%, reduction in risk. Cardiology meta-analyses demonstrate 18% reduction in serious vascular events with LDA. Non-responsiveness to aspirin (sometimes termed aspirin resistance) and variable clinical effectiveness are often attributed to suboptimal adherence. The aim of this review was to identify the scope of adherence assessments in RCTs evaluating aspirin effectiveness in cardiology and obstetrics and discuss the quality of information provided by current methods. We searched MEDLINE, EMBASE and the Cochrane Library, limited to humans and English language, for RCTs evaluating aspirin in cardiology; 14/03/13-13/03/16 and pregnancy 1957-13/03/16. Search terms; 'aspirin', 'acetylsalicylic acid' appearing adjacent to 'myocardial infarction' or 'pregnancy', 'pregnant', 'obstetric' were used. 38% (25/68) of obstetric and 32% (20/62) of cardiology RCTs assessed aspirin adherence and 24% (6/25) and 29% (6/21) of obstetric and cardiology RCTs, respectively, defined acceptable adherence. Semi-quantitative methods (pill counts, medication weighing) prevailed in obstetric RCTs (93%), qualitative methods (interviews, questionnaires) were more frequent in obstetrics (67%). Two obstetric RCTs quantified serum thromboxane B₂ and salicylic acid, but no quantitative methods were used in cardiology Aspirin has proven efficacy, but suboptimal adherence is widespread and difficult to accurately quantify. Little is currently known about aspirin adherence in pregnancy. RCTs evaluating aspirin effectiveness show over-reliance on qualitative adherence assessments vulnerable to inherent inaccuracies. Reliable adherence data is important to assess and optimise the clinical effectiveness of LDA. We propose that adherence should be formally assessed in future trials and that development of quantitative assessments may prove valuable for trial protocols.

Impact of USPSTF recommendations for aspirin for prevention of recurrent preeclampsia

BACKGROUND

The US Preventive Services Task Force recommends low-dose aspirin for the prevention of preeclampsia among women at high risk for primary occurrence or recurrence of disease. Recommendations for the use of aspirin for preeclampsia prevention were issued by the US Preventive Services Task Force in September 2014.

OBJECTIVES

The objective of the study was to evaluate the incidence of recurrent preeclampsia in our cohort before and after the US Preventive Services Task Force recommendation for aspirin for preeclampsia prevention.

STUDY DESIGN

This was a retrospective cohort study designed to evaluate the rates of recurrent preeclampsia among women with a history of preeclampsia. We utilized a 2-hospital, single academic institution database from August 2011 through June 2016. We excluded multiple gestations and included only the first delivery for women with multiple deliveries during the study period. The cohort of women with a history of preeclampsia were divided into 2 groups, before and after the release of the US Preventive Services Task Force 2014 recommendations. Potential confounders were accounted for in multivariate analyses, and relative risk and adjusted relative risk were calculated.

RESULTS

A total of 17,256 deliveries occurred during the study period. A total of 417 women had a documented history of prior preeclampsia: 284 women before and 133 women after the US Preventive Services Task Force recommendation. Comparing the before and after groups, the proportion of Hispanic women in the after group was lower and the method of payment differed between the groups (P <.0001). The prevalence of type 1 diabetes was increased in the after period, but overall rates of pregestational diabetes were similar (6.3% before vs 5.3% after [P > .05]). Risk factors for recurrent preeclampsia included maternal age >35 years (relative risk, 1.83; 95% confidence interval, 1.34-2.48), Medicaid insurance (relative risk, 2.08; 95% confidence interval, 1.15-3.78), type 2 diabetes (relative risk, 2.13; 95% confidence interval, 1.37-3.33), and chronic hypertension (relative risk, 1.96; 95% confidence interval, 1.44-2.66). The risk of recurrent preeclampsia was decreased by 30% in the after group (adjusted relative risk, 0.70; 95% confidence interval, 0.52-0.95).

CONCLUSION

Rates of recurrent preeclampsia among women with a history of preeclampsia decreased by 30% after release of the US Preventive Services Task Force recommendation for aspirin for preeclampsia prevention. Future prospective studies should include direct measures of aspirin compliance, gestational age at initiation, and explore the influence of race and ethnicity on the efficacy of this primary prevention.

Aspirin vs Heparin for the Prevention of Preeclampsia

Preeclampsia is a hypertensive disorder of pregnancy that remains a significant cause of maternal morbidity and mortality worldwide. Preeclampsia can be resolved by delivery, and most of the proposed preventive treatment approaches are based on processes involved in placental development in early pregnancy. Yet, none of these has been established in clinical practice. Low-dose aspirin is the most promising candidate, nevertheless; while some individual randomized controlled trials showed minimal or no statistically significant benefit, recent metanalyses showed that early initiation before 16 weeks of gestation is associated with prevention of early-onset preeclampsia and reduction in prevalence of perinatal death or morbidity of pregnant women. Heparin could be an alternative antithrombotic and anti-inflammatory median to prevent preeclampsia either alone or in combination with aspirin; however, results are conflicting concerning efficacy.

Antiplatelet therapy before or after 16 weeks' gestation for preventing preeclampsia: an individual participant data meta-analysis

BACKGROUND

The optimum time for commencing antiplatelet therapy for the prevention of preeclampsia and its complications is unclear. Aggregate data meta-analyses suggest that aspirin is more effective if given prior to 16 weeks' gestation, but data are limited because of an inability to place women in the correct gestational age subgroup from relevant trials.

OBJECTIVE

The objective of the study was to use the large existing individual participant data set from the Perinatal Antiplatelet Review of International Studies Collaboration to assess whether the treatment effects of antiplatelet agents on preeclampsia and its complications vary based on whether treatment is started before or after 16 weeks' gestation.

STUDY DESIGN

A meta-analysis of individual participant data including 32,217 women and 32,819 babies recruited to 31 randomized trials comparing low-dose aspirin or other antiplatelet agents with placebo or no treatment for the prevention of preeclampsia has been published previously. Using this existing data set, we performed a prespecified subgroup analysis based on gestation at randomization to antiplatelet agents before 16 weeks, compared with at or after 16 weeks, for 4 of the main outcomes prespecified in the Perinatal Antiplatelet Review of International Studies protocol: preeclampsia, death of baby, preterm birth before 34 weeks, and small-for-gestational-age baby. Individual participant data for the subgroups were combined in a meta-analysis using RevMan software. Heterogeneity was assessed with the I² statistic. The χ² test for interaction was used to assess statistically significant (P < .05) differences in treatment effect between subgroups.

RESULTS

There was no significant difference in the effects of antiplatelet therapy for women randomized before 16 weeks' gestation compared with those randomized at or after 16 weeks for any of the 4 prespecified outcomes: preeclampsia, relative risk, 0.90, (95% confidence interval, 0.79-1.03; 17 trials, 9241 women) for <16 weeks and relative risk, 0.90 (95% confidence interval, 0.83-0.98; 22 trials, 21,429 women) for ≥16 weeks (interaction test, P = .98); death of baby, relative risk, 0.89 (95% confidence interval, 0.73-1.09; 15 trials, 8626 women) for <16 weeks and relative risk, 0.92 (95% confidence interval, 0.79-1.07; 21 trials, 22,336 women) for ≥16 weeks (interaction test, P = .80); preterm birth prior to 34 weeks, relative risk, 0.90 (95% confidence interval, 0.77-1.04; 19 trials, 9155 women) for <16 weeks and relative risk, 0.91 (95% confidence interval, 0.82-1.00; 25 trials, 22,117 women) for ≥16 weeks (interaction test, P = .91); and small-for-gestational-age baby, relative risk, 0.76 (95% confidence interval, 0.61-0.94; 13 trials, 6393 women) for <16 weeks and relative risk, 0.95 (95% confidence interval, 0.84-1.08; 18 trials, 14,996 women) for ≥16 weeks (interaction test, P = .08).

CONCLUSION

The effect of low-dose aspirin and other antiplatelet agents on preeclampsia and its complications is consistent, regardless of whether treatment is started before or after 16 weeks' gestation. Women at an increased risk of preeclampsia should be offered antiplatelet therapy, regardless of whether they are first seen before or after 16 weeks' gestation.

How I treat essential thrombocythemia

Essential thrombocythemia (ET) is an indolent myeloproliferative neoplasm that may be complicated by vascular events, including both thrombosis and bleeding. This disorder may also transform into more aggressive myeloid neoplasms, in particular into myelofibrosis. The identification of somatic mutations of JAK2, CALR, or MPL, found in about 90% of patients, has considerably improved the diagnostic approach to this disorder. Genomic profiling also holds the potential to improve prognostication and, more generally, clinical decision-making because the different driver mutations are associated with distinct clinical features. Prevention of vascular events has been so far the main objective of therapy, and continues to be extremely important in the management of patients with ET. Low-dose aspirin and cytoreductive drugs can be administered to this purpose, with cytoreductive treatment being primarily given to patients at high risk of vascular complications. Currently used cytoreductive drugs include hydroxyurea, mainly used in older patients, and interferon α, primarily given to younger patients. There is a need for disease-modifying drugs that can eradicate clonal hematopoiesis and/or prevent progression to more aggressive myeloid neoplasms, especially in younger patients. In this article, we use a case-based discussion format to illustrate our approach to diagnosis and treatment of ET.

Pregnancy in women with thalassemia: challenges and solutions

Advances in treatment of thalassemia have led to the aging of thalassemic patients, and consequently concern about successful reproductive outcome is augmented. Although women with thalassemia intermedia only were considered competent of achieving pregnancy, case series reveal the willingness of both thalassemia major and thalassemia intermedia women to have a family. Pregnancy in general is characterized by dynamic multiple-system changes and increased susceptibility to oxidative stress, while homozygous, transfusion-dependent, β-thalassemia patients manifest cardiac, hepatic, endocrine, and metabolic disorders attributable to chronic anoxia and iron overload and thalassemia intermedia, usually nontransfused, is associated with augmented risk of thromboembolic events. Pregnancy in thalassemia should be considered a high risk for both mother and fetus, and favorable outcomes are the result of continuous preconception, antenatal, and postpartum assessment and management by a team of thalassemia experts.

Low dose aspirin and pregnancy: how important is aspirin resistance?

Antiplatelet agents are pivotal for prevention of coronary artery disease and cerebrovascular disease worldwide. Individual patient data meta-analysis indicates that low-dose aspirin causes a 10% risk reduction in pre-eclampsia for women at high individual risk. However, in the last 15 years it has emerged that a significant proportion of aspirin-treated individuals exhibit suboptimal platelet response, determined biochemically and clinically, termed 'aspirin non-responsiveness', 'aspirin resistance' and 'aspirin treatment failure'. More recently, investigation of aspirin responsiveness has begun in pregnant women. This review explores the history and clinical relevance of 'aspirin resistance' applied to high-risk obstetric populations.

TWEETABLE ABSTRACT

Is 'aspirin resistance' clinically relevant in high-risk obstetrics?

Preventing preeclampsia and its fetal complications with low-dose aspirin in East Asians and non-East Asians:A systematic review and meta-analysis

BACKGROUND

Low-dose aspirin can reduce the incidence of preeclampsia and intrauterine growth restriction (IUGR). However, the effects of ethnicity upon low-dose aspirin's efficacy has not been analyzed. Here, we comparatively evaluated the efficacy of low-dose aspirin in preventing preeclampsia and related fetal complications in East Asian and non-East Asian pregnant women at risk for preeclampsia.

METHODS

Several databases were searched for randomized controlled trials (RCTs) comparing low-dose aspirin with either placebo or no treatment in pregnant women at risk for preeclampsia. Odds ratios (ORs) and associated 95% confidence intervals (CIs) for preeclampsia and related fetal outcomes were tabulated.

RESULTS

Low-dose aspirin significantly reduced preeclampsia risk in both East Asians (OR = 0.20, 95% CI: 0.11-0.35) and non-East Asians (OR = 0.84, 95% CI: 0.77-0.92). Low-dose aspirin significantly reduced IUGR risk in East Asians (OR = 0.36, 95% CI: 0.20-0.67) but not in non-East Asians (OR = 0.85, 95% CI: 0.41-1.77). Low-dose aspirin did not significantly reduce the risk of cesarean section in either East Asians (OR = 0.67, 95% CI: 0.14-3.22) or non-East Asians (OR = 1.01, 95% CI: 0.86-1.19).

CONCLUSIONS

Low-dose aspirin is effective in reducing preeclampsia risk in both East Asians and non-East Asians and has differential effects in East Asians and non-East Asians with respect to IUGR.

Lack of Thromboxane Synthase Prevents Hypertension and Fetal Growth Restriction after High Salt Treatment during Pregnancy

Preeclampsia (PE) is a potentially fatal pregnancy-related hypertensive disorder characterized by poor placenta development that can cause fetal growth restriction. PE-associated pathologies, including thrombosis, hypertension, and impaired placental development, may result from imbalances between thromboxane A₂ (TXA₂) and prostacyclin. Low-dose aspirin, which selectively inhibits TXA₂ production, is used to prevent high-risk PE. However, the role of TXA₂ in aspirin-mediated protective effects in women with PE is not understood fully. In this study, we examined the role of prostanoids in PE using human samples and an induced PE mouse model. We demonstrated that the administration of salted drinking water (2.7% NaCl) to wild-type mice resulted in elevated placental TXA₂ synthase (TXAS) and plasma TXA₂, but not prostacyclin, levels, which was also found in our clinical PE placenta samples. The high salt-treated wild-type pregnant mice had shown unchanged maternal body weight, hypertension (MAP increase 15 mmHg), and decreased pup weight (~50%) and size (~24%), but these adverse effects were ameliorated in TXAS knockout (KO) mice. Moreover, increased expression of interleukin-1β and downstream phosphorylated-p38-mitogen-activated protein kinase were concordant with apoptosis induction in the placentas of salt water-treated wild-type mice. These alterations were not observed in TXAS KO mice. Together, our data suggest that TXA₂ depletion has anti-PE effects due to the prevention of hypertension and placental damage through downregulation of the interleukin-1β pathway.

Subchorionic hematomas are increased in early pregnancy in women taking low-dose aspirin

OBJECTIVE

To determine the frequency of subchorionic hematomas (SCH) in first-trimester ultrasound examinations of patients with infertility and recurrent pregnancy loss (RPL) and in patients from a general obstetric population. To determine if the method of assisted reproduction utilized or the use of anticoagulants, such as heparin and aspirin (ASA), influenced frequency of SCH.

DESIGN

Prospective, cohort study.

SETTING

Fertility clinic and general obstetrics clinic.

PATIENT(S)

Five hundred and thirty-three women who were pregnant in the first-trimester.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE(S)

Frequencies of subchorionic hematomas in women based on diagnosis, use of anticoagulants, and fertility treatment.

RESULT(S)

SCH were identified in 129/321 (40.2%) in the study group compared to 23/212 (10.9%) in the control group. Fertility diagnosis and the use of heparin did not appear to affect the frequency of SCH in the first trimester; however, SCH occurred at an almost four-fold increase in patients taking ASA compared to those not taking ASA, regardless of fertility diagnosis or method of fertility treatment.

CONCLUSION(S)

The use of ASA may be associated with an increased risk of developing a SCH during the first trimester. The increased frequencies of SCH in pregnancies of patients attending a fertility clinic compared to women from a general obstetrical practice was highly correlated with the use of ASA.