Cardiovascular conditions have become the leading cause of maternal mortality in high-income settings.¹ Hypertensive disorders of pregnancy (HDP), occurring in 10% of pregnancies worldwide, remain major contributors to pregnancy-related cardiovascular morbidity.^{1, 2} Thus, a better understanding of the contribution of HDP to pregnancy-related cardiovascular complications is critical to reducing the incidence of maternal morbidity and mortality going forward.

In their population-based cohort study, Lee and colleagues³ explored the association between HDP subtypes (i.e. chronic hypertension, gestational hypertension, preeclampsia with mild features, preeclampsia with severe features, superimposed preeclampsia and eclampsia) and cardiovascular mortality, including deaths related to heart disease and stroke, from the time of delivery up until the first calendar year postpartum. Using a large, nationally representative sample of patients in the US (Nationwide Readmission Database [NRD]) with follow-up in the first year postpartum, they were able to address the limitations of prior work.³ Importantly, by highlighting the associations between specific subtypes of HDP (except gestational hypertension) and cardiovascular mortality (adjusted hazard ratios range: 1.96 to 58.55, with the highest risk for eclampsia), their work illustrates the persistent contribution of HDP to maternal mortality during pregnancy and postpartum despite advances in obstetric care.³

While this study emphasises the short-term cardiovascular burden associated with subtypes of HDP, the observed associations between HDP and cardiovascular mortality may have been underestimated. The restriction of the study population to women without pre-existing cardiovascular disease (of note, patients with congenital heart disease were not excluded) could have attenuated the observed associations since prior evidence has shown an increased risk of mortality among women with structural heart disease and co-occurring HDP.⁴ Moreover, while cardiovascular diagnoses included in the outcome were comprehensive, they did not capture indicators of ruptured aneurysm.⁵ Lastly, the sensitivity of ICD-9 and 10 codes for cardiovascular severe maternal morbidity as a composite outcome, particularly in the context of preeclampsia, has previously been found to be low, ranging from 10% to 50%.⁵ Therefore, cardiovascular events may have been misclassified, potentially attenuating the true association between HDP and cardiovascular-related deaths.

To assess the cardiovascular nature of reported deaths, all pregnancy-related in-hospital deaths in the same calendar year as the birth were identified and stratified into those with co-incident heart disease and stroke. However, the direct link between cardiovascular events and mortality could not be ascertained. While individuals with cardiovascular diagnoses captured prior to pregnancy were excluded from the study population, cardiovascular diagnoses captured during pregnancy included in the “heart disease-related deaths” category could include diagnoses corresponding to prevalent, chronic conditions (e.g. ischaemic heart disease and atherosclerotic heart disease), which did not necessarily represent acute events. Although deaths in the context of these cardiovascular conditions were being captured, these deaths may not have directly resulted from them. For instance, upon review of granular clinical data during a confidential inquiry, a patient with stable hypertensive heart disease who died following severe sepsis may have been classified as having had an infection-related death. While her death occurred in the context of an underlying heart condition, she may not have been considered as having had a heart disease-related death. Since centralised reporting systems and confidential enquiries are not systematically in place to perform a detailed assessment of pregnancy-related deaths, we may need to continue to rely on administrative datasets (like the NRD) to assess causes of maternal mortality at the population level with a certain degree of misclassification. While the authors highlighted the increased accuracy of using in-hospital mortality based on administrative datasets such as the NRD compared to estimates based on vital statistics data using the standardised pregnancy checkbox on death certificates,³ the accuracy of underlying causes of maternal mortality identified using these datasets must be optimised prior to their use for surveillance purposes.

Severe maternal morbidity is comprised of a set of unexpected maternal outcomes related to pregnancy, labour, childbirth and the postpartum period resulting in severe illness, prolonged hospitalisation and/or long-term disability.⁶ Since severe maternal morbidity may be on the pathway to maternal mortality,⁶ the use of indicators of severe cardiovascular morbidity (e.g., acute myocardial infarction), in addition to underlying chronic cardiovascular diagnoses (e.g., coronary artery disease), could improve the accuracy of reporting of causes of mortality, emulating the cause-of-death section of death certificates.⁷ However, this does require further exploration using well-designed validation studies. While indicators of severe maternal morbidity have been standardised for use in surveillance and research, indicators used to capture causes of maternal mortality are lagging. As a result, indicators used to identify cardiovascular mortality cases differed from those used to identify cardiovascular subtypes of severe maternal morbidity events, as defined by the Centers for Disease Control and Prevention.^{5, 8} To ensure accurate reporting and implementation of preventative measures geared towards reducing cardiovascular morbidity and mortality, there is an urgent need to harmonise the assessment of cardiovascular causes of severe maternal morbidity and mortality.

Finally, due to the process for data collection in the NRD, the ability to observe events up to 1 year postpartum was not possible for all women delivering after January, resulting in missed events. This raises concerns regarding the utility of data sources that capture events based on calendar year, since the postpartum period is known to be a high-risk period for mortality for individuals with HDP and cardiovascular complications.⁹ However, the increased risk in the earlier periods of follow-up (<60 days postpartum) suggests that the extent of the attenuation of the observed associations may be less of a concern. While, Lee and colleagues³ demonstrated the added value of conducting maternal mortality surveillance using routine administrative datasets with extended follow-up beyond 42 days postpartum, the results need to be interpreted in light of the potential limitations arising from the quality of the data source.

The strong association between HDP subtypes and cardiovascular mortality in this study highlights the need to extend postpartum care and health insurance coverage for pregnant individuals later than the early postpartum period to prevent maternal cardiovascular deaths.³ In addition, concerted efforts are required to reduce the risk of cardiovascular-related morbidity and mortality in women with HDP, including strategies to raise awareness among clinicians and patients regarding the heightened risk in these individuals, interventions to harmonise cardiovascular care across the pregnancy continuum, and increased availability of programs that allow for continual follow-up in the first year postpartum to align with current clinical recommendations.¹⁰

The findings by Lee and colleagues³ expand the current evidence on the association between HDP subtypes and cardiovascular mortality, including the postpartum period, a crucial period for the prevention of HDP-related short and long-term cardiovascular morbidity and mortality. This work highlights the need for future research focused on the validation of underlying causes of maternal mortality and the need for higher quality sources of epidemiological data to optimise surveillance of maternal mortality.

心血管疾病已成为高收入地区孕产妇死亡的主要原因。¹妊娠期高血压疾病 (HDP) 发生在全世界 10% 的妊娠中，它仍然是妊娠相关心血管疾病的主要原因。^{1, 2}因此，更好地了解 HDP 对妊娠相关心血管并发症的影响对于降低未来孕产妇发病率和死亡率至关重要。

在他们的基于人群的队列研究中，Lee 及其同事³探讨了 HDP 亚型（即慢性高血压、妊娠期高血压、轻度子痫前期、重度子痫前期、子痫前期和子痫叠加）与心血管死亡率（包括与心脏相关的死亡）之间的关联。疾病和中风，从分娩时到产后第一年。通过使用具有全国代表性的美国患者样本（全国再入院数据库 [NRD]）并在产后第一年进行随访，他们能够解决之前工作的局限性。³重要的是，通过强调 HDP 的特定亚型（妊娠期高血压除外）与心血管死亡率之间的关联（调整后的风险比范围：1.96 至 58.55，子痫风险最高），他们的工作说明了 HDP 对孕产妇死亡率的持续影响。尽管产科护理取得了进步，但怀孕和产后仍然如此。³

虽然这项研究强调与 HDP 亚型相关的短期心血管负担，但观察到的 HDP 与心血管死亡率之间的关联可能被低估了。将研究人群限制为未患有心血管疾病的女性（值得注意的是，不排除患有先天性心脏病的患者）可能会减弱观察到的关联性，因为先前的证据表明患有结构性心脏病和心脏病的女性的死亡风险增加。同时发生的HDP。⁴此外，虽然结果中包含的心血管诊断很全面，但它们并未捕获动脉瘤破裂的指标。⁵最后，之前发现 ICD-9 和 10 代码对心血管严重孕产妇发病作为复合结果的敏感性较低，特别是在先兆子痫的情况下，敏感性较低，范围为 10% 至 50%。⁵因此，心血管事件可能被错误分类，可能削弱 HDP 与心血管相关死亡之间的真实关联。

为了评估报告的死亡的心血管性质，确定了出生同一日历年内所有与妊娠相关的院内死亡，并将其分层为同时患有心脏病和中风的死亡。然而，无法确定心血管事件与死亡率之间的直接联系。虽然在怀孕前进行心血管诊断的个体被排除在研究人群之外，但在怀孕期间进行的心血管诊断（包括在“心脏病相关死亡”类别中）可能包括与流行的慢性疾病（例如缺血性心脏病和动脉粥样硬化性心脏病）相对应的诊断。 ），这并不一定代表急性事件。尽管这些心血管疾病导致的死亡被记录下来，但这些死亡可能并不是由这些疾病直接造成的。例如，在保密调查期间审查详细的临床数据后，一名因严重败血症而死亡的稳定型高血压心脏病患者可能被归类为与感染相关的死亡。虽然她的死亡是在潜在的心脏病的背景下发生的，但她可能不被认为是与心脏病相关的死亡。由于没有系统地建立集中报告系统和保密调查来对妊娠相关死亡进行详细评估，我们可能需要继续依靠行政数据集（如 NRD）来评估人口层面孕产妇死亡的原因，一定程度的误分类。虽然作者强调，与使用死亡证明上标准化怀孕复选框的基于生命统计数据的估计相比，使用基于 NRD 等行政数据集的院内死亡率的准确性更高，3 使用这些数据确定的孕产妇死亡根本原因^的准确性数据集在用于监视目的之前必须进行优化。

严重孕产妇发病率由一系列与怀孕、临产、分娩和产后期相关的意外孕产妇结局组成，导致严重疾病、长期住院和/或长期残疾。⁶由于严重的孕产妇发病率可能会导致孕产妇死亡，⁶除了潜在的慢性心血管疾病（例如，冠状动脉疾病）之外，使用严重心血管发病率（例如，急性心肌梗死）指标可以提高准确性报告死亡原因，效仿死亡证明的死因部分。⁷然而，这确实需要使用精心设计的验证研究进行进一步探索。虽然严重孕产妇发病率指标已标准化，用于监测和研究，但用于确定孕产妇死亡原因的指标却滞后。因此，用于识别心血管死亡病例的指标与疾病控制和预防中心定义的用于识别严重孕产妇发病事件心血管亚型的指标不同。^{5, 8}为了确保准确报告和实施旨在降低心血管发病率和死亡率的预防措施，迫切需要协调对严重孕产妇发病率和死亡率的心血管原因的评估。

最后，由于 NRD 的数据收集流程，对于所有 1 月后分娩的女性来说，不可能观察到产后 1 年的事件，从而导致错过事件。这引起了人们对根据日历年捕获事件的数据源的实用性的担忧，因为已知产后期是 HDP 和心血管并发症患者死亡的高风险期。⁹然而，早期随访期间（产后 60 天以内）的风险增加表明，观察到的关联性的减弱程度可能不太值得关注。虽然 Lee 及其同事³证明了使用常规管理数据集进行孕产妇死亡率监测并在产后 42 天以上进行长期随访具有附加价值，但需要根据数据源质量带来的潜在限制来解释结果。

本研究中 HDP 亚型与心血管死亡率之间的密切相关性凸显了需要在产后早期之后扩大孕妇的产后护理和健康保险覆盖范围，以预防孕产妇心血管死亡。³此外，需要共同努力降低 HDP 女性心血管相关发病率和死亡率的风险，包括采取策略提高临床医生和患者对这些个体风险增加的认识，采取干预措施协调整个妊娠过程中的心血管护理，并增加了允许在产后第一年进行持续随访的计划的可用性，以符合当前的临床建议。¹⁰

Lee 及其同事的研究结果³扩展了 HDP 亚型与心血管死亡率之间关联的现有证据，包括产后期，这是预防 HDP 相关短期和长期心血管发病率和死亡率的关键时期。这项工作强调了未来研究的重点是验证孕产妇死亡的根本原因，以及需要更高质量的流行病学数据来源来优化孕产妇死亡率的监测。