Strategies for Prescribing Aspirin to Prevent Preeclampsia: A Cost-Effectiveness Analysis

Aspirin for preeclampsia prevention in low- and middle-income countries: mind the gaps

Preeclampsia is a syndrome that continues to be a major contributor to maternal and neonatal mortality, especially in low-income countries. Low-dose aspirin reduces the risk of preeclampsia, but the mechanism is still unknown. Risk factors to identify women at risk of preeclampsia are based on clinical characteristics. Women identified as high-risk would benefit from aspirin treatment initiated, preferably at the end of the first trimester. Current efforts have largely focused on developing screening algorithms that incorporate clinical risk factors, maternal biomarkers, and uterine artery Doppler evaluated in the first trimester. However, most studies on preeclampsia are conducted in high-income settings, raising uncertainties about whether the information gained can be totally applied in low-resource settings. In low- and middle-income countries, lack of adequate antenatal care and late commencement of antenatal care visits pose significant challenges for both screening for preeclampsia and initiating aspirin treatment. Furthermore, the preventive effect of first-trimester screening based on algorithms and subsequent aspirin treatment is primarily seen for preterm preeclampsia, and reviews indicate minimal or no impact on reducing the risk of term preeclampsia. The lack of evidence regarding the effectiveness of aspirin in preventing term preeclampsia is a crucial concern, as 75% of women will develop this subtype of the syndrome. Regarding adverse outcomes, low-dose aspirin has been linked to a possible higher risk of postpartum hemorrhage, a condition as deadly as preeclampsia in many low- and middle-income countries. The increased risk of postpartum hemorrhage among women in low-income settings should be taken into consideration when discussing which pregnant women would benefit from the use of aspirin and the ideal aspirin dosage for preventing preeclampsia. In addition, women's adherence to aspirin during pregnancy is crucial for determining its effectiveness and complications, an aspect often overlooked in trials. In this review, we analyze the knowledge gaps that must be addressed to safely increase low-dose aspirin use in low- and middle-income countries, and we propose directions for future research.

Prevention of preeclampsia

Preeclampsia is a relatively common pregnancy complication and constitutes a major cause of morbidity and mortality for mothers and children worldwide. It disproportionally affects low-resource countries. Appropriate identification of individuals at increased risk and prevention of the disease and its complications remain healthcare and research priorities, and the investigation of potential interventions to prevent preeclampsia has driven much of the obstetric research in recent decades. In this article, we review the scientific literature on the topic, highlighting established benefits and remaining questions regarding different non-pharmacological and pharmacological strategies, including exercise, the timing of birth, aspirin and calcium use, among others, as well as potential novel therapies under investigation.

First trimester screening for pre-eclampsia and targeted aspirin prophylaxis: a cost-effectiveness cohort study

OBJECTIVE

Investigate cost-effectiveness of first trimester pre-eclampsia screening using the Fetal Medicine Foundation (FMF) algorithm and targeted aspirin prophylaxis in comparison with standard care.

DESIGN

Retrospective observational study.

SETTING

London tertiary hospital.

POPULATION

5957 pregnancies screened for pre-eclampsia using the National Institute for Health and Care Excellence (NICE) method.

METHODS

Differences in pregnancy outcomes between those who developed pre-eclampsia, term pre-eclampsia and preterm pre-eclampsia were compared by the Kruskal-Wallis and Chi-square tests. The FMF algorithm was applied retrospectively to the cohort. A decision analytic model was used to estimate costs and outcomes for pregnancies screened using NICE and those screened using the FMF algorithm. The decision point probabilities were calculated using the included cohort.

MAIN OUTCOME MEASURES

Incremental healthcare costs and QALY gained per pregnancy screened.

RESULTS

Of 5957 pregnancies, 12.8% and 15.9% were screen-positive for development of pre-eclampsia using the NICE and FMF methods, respectively. Of those who were screen-positive by NICE recommendations, aspirin was not prescribed in 25%. Across the three groups, namely, pregnancies without pre-eclampsia, term pre-eclampsia and preterm pre-eclampsia there was a statistically significant trend in rates of emergency caesarean (respectively 21%, 43% and 71.4%; P < 0.001), admission to neonatal intensive care unit (NICU) (5.9%, 9.4%, 41%; P < 0.001) and length of stay in NICU. The FMF algorithm was associated with seven fewer cases of preterm pre-eclampsia, cost saving of £9.06 and QALY gain of 0.00006/pregnancy screened.

CONCLUSIONS

Using a conservative approach, application of the FMF algorithm achieved clinical benefit and an economic cost saving.

Aspirin in Pregnancy

Preeclampsia is associated with significant perinatal morbidity and mortality. Aspirin has been long purported and extensively studied for prevention of preeclampsia. For this reason, the U.S. Preventive Services Task Force, the American College of Obstetricians and Gynecologists, and the Society for Maternal-Fetal Medicine recommend its use in pregnancy for preeclampsia prevention in those at high risk. Yet, much controversy exists regarding optimal use in pregnancy with guidelines across global organizations varying. In this narrative review, we summarize the published literature related to the safety, optimal dose, and timing and duration of use of aspirin, as well as other indications for which aspirin has been studied in pregnancy.

Low-Dose Aspirin after ASPRE-More Questions Than Answers? Current International Approach after PE Screening in the First Trimester

Preeclampsia (PE) is a multi-factorial disorder of pregnancy, and it continues to be one of the leading causes of fetal and maternal morbidity and mortality worldwide. Aspirin is universally recommended for high-risk women to reduce preeclampsia risk. The purpose of this review is to summarize the recommendations of various scientific societies on predicting preeclampsia and their indications for the inclusion of acetylsalicylic acid (ASA) prophylaxis. Fourteen guidelines were compared. The recommended dose, screening method, and gestational age at the start of the test vary depending on the recommendation. The societies are inclined to recommend using increasingly higher doses (>75 mg) of ASA, with many encouraging doses from 100 mg upward. Most societies indicate that the optimal time for implementing aspirin is prior to 16 weeks' gestation. Following the publication of the Aspirin for Evidence-Based Preeclampsia Prevention (ASPRE) trial results and other papers evaluating the Fetal Medicine Foundation (FMF) screening model, a large number of societies have changed their recommendations from those based on risk factors alone to the ones based on the risk assessment proposed by the FMF. This allows for the detection of a high-risk pregnancy population in whom aspirin will be remarkably effective in preventing preterm PE, thereby decreasing maternal and fetal morbidity.

Perspectives on the Use of Placental Growth Factor (PlGF) in the Prediction and Diagnosis of Pre-Eclampsia: Recent Insights and Future Steps

Pre-eclampsia (PE) is a complex multisystem disease of pregnancy that is becoming increasingly recognized as a state of angiogenic imbalance characterized by low concentrations of placental growth factor (PlGF) and elevated soluble fms-like tyrosine kinase (sFlt-1). PlGF is a protein highly expressed by the placenta with vasculogenic and angiogenic properties, which has a central role in spiral artery remodeling and the development of a low-resistance placental capillary network. PlGF concentrations are significantly lower in women with preterm PE, and these reduced levels have been shown to precede the clinical onset of disease. Subsequently, the clinical utility of maternal serum PlGF has been extensively studied in singleton gestations from as early as 11 to 13 weeks' gestation, utilizing a validated multimarker prediction model, which performs superiorly to the National Institute for Health and Care Excellence (NICE) and American College of Obstetricians and Gynecologists (ACOG) guidelines in the detection of preterm PE. There is extensive research highlighting the role of PlGF-based testing utilizing commercially available assays in accelerating the diagnosis of PE in symptomatic women over 20 weeks' gestation and predicting time-to-delivery, allowing individualized risk stratification and appropriate antenatal surveillance to be determined. "Real-world" data has shown that interpretation of PlGF-based test results can aid clinicians in improving maternal outcomes and a growing body of evidence has implied a role for sFlt-1/PlGF in the prognostication of adverse pregnancy and perinatal events. Subsequently, PlGF-based testing is increasingly being implemented into obstetric practice and is advocated by NICE. This literature review aims to provide healthcare professionals with an understanding of the role of angiogenic biomarkers in PE and discuss the evidence for PlGF-based screening and triage. Prospective studies are warranted to explore if its implementation significantly improves perinatal outcomes, explore the value of repeat PlGF testing, and its use in multiple pregnancies.

Effectiveness of Different Algorithms and Cut-off Value in Preeclampsia First Trimester Screening

Results

For the cut-off point >1 : 150, 86 women at an increased risk of eo-PE using algorithm 1 were identified. Of these 86 patients, 83 (96%) were identified using algorithm 2, 62 (72%) using algorithm 3, and 60 (69%) using algorithm 4. In addition, it was demonstrated that between 21% and 29% of women at a low risk of eo-PE could be given acetylsalicylic acid if a screening test was used that did not account for PlGF.

Conclusions

In order to provide the highest level of health care to pregnant women, it is extremely important that full screening for eo-PE should be ensured. The cheapest algorithm based only on MAP and UtPI resulted in our patients being unnecessarily exposed to complications.

Prevention of preeclampsia with aspirin

Preeclampsia is defined as hypertension arising after 20 weeks of gestational age with proteinuria or other signs of end-organ damage and is an important cause of maternal and perinatal morbidity and mortality, particularly when of early onset. Although a significant amount of research has been dedicated in identifying preventive measures for preeclampsia, the incidence of the condition has been relatively unchanged in the last decades. This could be attributed to the fact that the underlying pathophysiology of preeclampsia is not entirely understood. There is increasing evidence suggesting that suboptimal trophoblastic invasion leads to an imbalance of angiogenic and antiangiogenic proteins, ultimately causing widespread inflammation and endothelial damage, increased platelet aggregation, and thrombotic events with placental infarcts. Aspirin at doses below 300 mg selectively and irreversibly inactivates the cyclooxygenase-1 enzyme, suppressing the production of prostaglandins and thromboxane and inhibiting inflammation and platelet aggregation. Such an effect has led to the hypothesis that aspirin could be useful for preventing preeclampsia. The first possible link between the use of aspirin and the prevention of preeclampsia was suggested by a case report published in 1978, followed by the first randomized controlled trial published in 1985. Since then, numerous randomized trials have been published, reporting the safety of the use of aspirin in pregnancy and the inconsistent effects of aspirin on the rates of preeclampsia. These inconsistencies, however, can be largely explained by a high degree of heterogeneity regarding the selection of trial participants, baseline risk of the included women, dosage of aspirin, gestational age of prophylaxis initiation, and preeclampsia definition. An individual patient data meta-analysis has indicated a modest 10% reduction in preeclampsia rates with the use of aspirin, but later meta-analyses of aggregate data have revealed a dose-response effect of aspirin on preeclampsia rates, which is maximized when the medication is initiated before 16 weeks of gestational age. Recently, the Aspirin for Evidence-Based Preeclampsia Prevention trial has revealed that aspirin at a daily dosage of 150 mg, initiated before 16 weeks of gestational age, and given at night to a high-risk population, identified by a combined first trimester screening test, reduces the incidence of preterm preeclampsia by 62%. A secondary analysis of the Aspirin for Evidence-Based Preeclampsia Prevention trial data also indicated a reduction in the length of stay in the neonatal intensive care unit by 68% compared with placebo, mainly because of a reduction in births before 32 weeks of gestational age with preeclampsia. The beneficial effect of aspirin has been found to be similar in subgroups according to different maternal characteristics, except for the presence of chronic hypertension, where no beneficial effect is evident. In addition, the effect size of aspirin has been found to be more pronounced in women with good compliance to treatment. In general, randomized trials are underpowered to investigate the treatment effect of aspirin on the rates of other placental-associated adverse outcomes such as fetal growth restriction and stillbirth. This article summarizes the evidence around aspirin for the prevention of preeclampsia and its complications.