Association between hypertensive disorders of pregnancy and cardiovascular diseases within 24 months’ postpartum

Abstract

Background

Despite the well-known association between hypertensive disorders of pregnancy (HDP) and cardiovascular disease, there is limited data on which specific cardiovascular diagnoses have the greatest risk profiles during the first 24 months’ postpartum. Most existing data on hypertensive disorders of pregnancy and short-term cardiovascular disease risk is limited to the immediate postpartum period; however, it is critical to determine cardiovascular disease risk up to 24 months’ postpartum to inform cardiovascular disease screening protocols during the extended postpartum period.

Objective

We aimed to delineate the risk of significant cardiovascular diagnoses in the first 24 months’ postpartum among patients with HDP compared with patients without HDP.

Study Design

Our longitudinal population-based study included pregnant individuals with deliveries during 2007–2019 in the Maine Health Data Organization’s All Payer Claims Data. We excluded those with pre-existing cardiovascular disease, with multifetal gestations, or without continuous insurance during pregnancy. HDP and cardiovascular disease (categorized by specific condition: heart failure, ischemic heart disease, arrhythmia/cardiac arrest, cardiomyopathy, cerebrovascular disease/stroke, and new chronic hypertension) were identified by ICD 9/10 diagnosis codes. Cox proportional hazards models were used to estimate hazard ratios (HR), adjusting for potential confounding factors.

Results

Of the 119,422 pregnancies examined, the cumulative risk of cardiovascular disease within 24 months’ postpartum for those with HDP vs. without HDP was 0.6% vs. 0.2% for heart failure, 0.3% vs. 0.1% for ischemic heart disease, 0.2% vs. 0.2% for arrhythmia/cardiac arrest, 0.6% vs. 0.2% for cardiomyopathy, 0.8% vs. 0.4% for cerebrovascular disease/stroke, 1.6% vs. 0.7% for severe cardiac disease (composite outcome of heart failure, cerebrovascular disease/stroke, or cardiomyopathy), and 9.7% vs. 1.5% for new chronic hypertension. After adjustment for potential confounders, those with HDP had increased risk of heart failure, cerebrovascular disease, cardiomyopathy, and severe cardiac disease within the first 24 months’ postpartum (adjusted HR (aHR) 2.81 (95% CI 1.90–4.15), aHR 1.43 (95% CI 1.07–1.91), aHR 2.90 (95% CI 1.96–4.27), and aHR 1.90 (95% CI 1.54–2.30), respectively) as compared to those without HDP. In addition, those with HDP had an increased risk for new chronic hypertension diagnosed after 42 days’ postpartum, (aHR 7.29 (95% CI 6.57–8.09)). There was no association between HDP and ischemic heart disease (aHR 0.92 (95% CI 0.55–1.54) or cardiac arrest/arrhythmia (aHR 0.90 (95% CI 0.52–1.57). In addition, among women with HDP, the highest proportion of first cardiovascular disease diagnoses occurred during the first month postpartum for cardiomyopathy (44%), heart failure (39%), cerebrovascular disease/stroke (39%), and severe cardiac disease (41%).

Conclusion

Patients with HDP had an increased risk for development of new chronic hypertension, heart failure, cerebrovascular disease, and cardiomyopathy within 24 months’ postpartum. There was no association between HDP and ischemic heart disease or cardiac arrest/arrhythmia. Patients with HDP need targeted early postpartum interventions and increased monitoring over the first 24 months. This may preserve long term health and improve maternal and neonatal outcomes in a subsequent pregnancy.

Introduction

Cardiovascular disease (CVD) is the leading cause of death among women in the US, accounting for 1 in 5 deaths.¹ It is well established that hypertensive disorders of pregnancy (HDP) confer a substantial increased risk of long-term cardiovascular morbidity and mortality decades after delivery.^2–5 However, in the immediate postpartum period, most existing data on short-term cardiovascular disease risk is from 6 weeks’ postpartum up to 12 months’.^6–12 There is very limited data on CVD risk up to 24 months’ postpartum.

Because pregnancy is a vascular stress test, the initial 24 months’ postpartum offers a unique window of opportunity to identify women at greatest risk, and implement life-saving cardiovascular screening and prevention.^6,7 In order to reduce cardiovascular morbidity and mortality, identification of early risk factors and implementation of individualized prevention strategies during the postpartum period are critical.^6,13–16 The American Heart Association (AHA) and American College of Obstetricians and Gynecologists (ACOG) issued urgent calls to action to address this staggering problem of cardiovascular morbidity and mortality for women.^17–19

Unfortunately, the optimal postpartum screening strategy for women with HDP remains unclear. Currently, ACOG recommends women with HDP have long-term follow-up postpartum with more frequent visits with their primary care provider and a CVD risk assessment, which includes assessment of the effect of social determinants of health on cardiometabolic disease.^20–23 Despite a few cardiovascular screening clinics with evaluations between 6–12 months’ postpartum, including the Mothers Program Maternal Health Clinic in Ontario, Canada, these CVD screening clinics are not considered standard of care in the United States.^6,15,16,24 This is in part due to the lack of financial reimbursement for patients who lose healthcare insurance after 6 weeks’ postpartum.¹⁸ In addition, it is unclear the optimal timing for CVD risk assessment postpartum due to the lack of identification of specific CVD risks within 24 months’ postpartum and which CVD conditions occur soonest after delivery. Most prior studies have focused either on 1–2 cardiovascular diseases such as heart failure or coronary artery disease or a composite of many cardiovascular diseases.^2–5 In order to effectively screen for cardiovascular morbidity and mortality among women, we must first be able to identify the specific CVD diagnoses that occur as early as 24 months’ postpartum.¹⁹

Therefore, we sought to delineate the risk and timing of onset of key cardiovascular diagnoses in the first 24 months’ postpartum among patients with HDP compared with patients without HDP.

Materials and Methods

We performed a longitudinal population-based study of multiparous and nulliparous individuals with singleton livebirth or stillbirth gestations to determine the risk of significant cardiovascular diagnoses in the first 24 months’ postpartum, comparing patients with HDP to those without HDP. Data from the Maine Health Data Organization’s All Payer Claims Data (APCD) was used and included pregnant individuals with deliveries in Maine that were paid for by either private or public insurers.²⁵ The largest possible sample size in our database, 13 years of deliveries, was utilized in order to maximize power. The All Payer Claims Data includes both facility and professional claims for hospital inpatient and outpatient encounters and office visits.²⁵ The International Classification of Diseases, Clinical Modification (ICD-CM) diagnosis and procedure codes, current procedural terminology (CPT) codes, and the Medicare Severity Diagnosis Related Group (MS-DRG) classification system were used to identify deliveries during the study period. APCD must meet internal quality standards before being released for analysis.²⁵

HDP included one or more of the following diagnoses: gestational hypertension, preeclampsia without severe features, preeclampsia with severe features, superimposed preeclampsia with or without severe features, or eclampsia.²⁰ Claims met the criteria for HDP if there were 2 or more outpatient visits (to avoid patients presenting for rule-out HDP) with non-severe HDP diagnosis codes or at least 1 inpatient visit with non-severe or severe HDP diagnosis codes from 20 weeks of gestation until 42 days’ postpartum. HDP were defined using a previously published method using ICD-9 codes.²⁶ The ICD-9 codes were then cross-walked to the corresponding ICD-10 diagnosis codes (Appendix 1).

The primary outcome was cardiovascular disease, categorized into 6 sub-categories: heart failure, ischemic heart disease, cerebrovascular disease/stroke, arrhythmia/cardiac arrest, cardiomyopathy, and new chronic hypertension. In addition, given the anticipated rarity of some of the CVD outcomes, a composite outcome of severe cardiac disease was developed a priori that included heart failure, cerebrovascular disease/stroke, and cardiomyopathy. We used previously published cross-walked ICD 9/10 code lists (Cartus et al; Ackerman et al) and added “not otherwise specified” cardiovascular disease diagnosis codes based on review by Maternal Fetal Medicine physician study authors (C.A.B, H.S.L.) (Appendix 1).^27,28 They were defined from the delivery date until 24 months’ postpartum.

In contrast, new chronic hypertension was defined only from 43 days’ postpartum until 24 months’ postpartum because hypertension within 42 days of delivery is considered a HDP.^29,30 The Centers for Disease Control and Prevention code list was used to define new chronic hypertension.³¹

Socioeconomic factors and access to care were estimated by linking the All Payer Claims Data to publicly available community-level information. ZIP-code level data on the median percentage of residents living below federal poverty level, of non-White race/ethnicity, and who were adults with less than college educational attainment were identified from the American Community Survey 5-year ZIP-code files.³² To assess population-level access to care measures, information on the number of general practice and medical specialties physicians per capita from the Area Health Resources Files were linked by county Federal Information Processing Standard code.³³ Insurance status was assessed using the All Payer Claims Data eligibility file. People were classified as Medicaid insured if they were enrolled in Medicaid during their delivery month.³⁴ Otherwise, they were classified as insured by commercial insurance or Medicare based on delivery month enrollment information.

Cox proportional hazard models were used to estimate hazard ratios and 95% confidence intervals for the time to first diagnosis for each of the 6 cardiovascular conditions in the first 24 months’ postpartum. Models were adjusted for potential confounding factors, including maternal age at time of delivery, pre-pregnancy depression (diagnosed from one year prior to conception to 6 weeks of gestation), pre-existing chronic hypertension (diagnosed from one year prior to conception to 20 weeks of gestation), pre-pregnancy diabetes, obesity, smoking, nulliparity, pregnancy number in dataset (as a proxy for parity), year of delivery, Medicaid coverage during pregnancy, county-level measures, ZIP-code level measures (including percentage of population with non-White race/ethnicity), prenatal depression (diagnosed from 6 weeks’ gestation until delivery), and gestational diabetes. Each model excluded records with any diagnosis before pregnancy of the cardiovascular conditions being examined postpartum, and records with gestational age <20 weeks (i.e. miscarriages erroneously coded as livebirths or stillbirths), non-Maine residence, multifetal gestation, those without evidence of insurance in the month of delivery, those with implausible time to next pregnancy (<60 days), and those without health insurance during pregnancy and through the first 2 months’ postpartum. We excluded multifetal pregnancies because of their increased risk of pregnancy complications such as HDP and cardiovascular complications, including cardiac arrest, compared to their singleton counterparts.^35,36 Those with pre-existing chronic hypertension were excluded from models examining new postpartum chronic hypertension, but for the other CVD outcomes, persons with pre-existing chronic hypertension or other cardiovascular conditions during pregnancy were not excluded in the primary analysis. Observations were censored upon loss of health insurance coverage, start of next pregnancy, or at 24 months, whichever came first. As a sensitivity analysis, models were rerun after stratification by pre-existing chronic hypertension to see if the effect of HDP on CVD outcomes differed by this key pre-existing medical condition. To visualize the survival curves, we used inverse-probability-of-treatment-weighted Cox proportional hazard models.³⁷ All time-to-event analyses used month since delivery as the time scale.

Results

Out of the 166,053 unique pregnancies in the Maine Health Data Organization’s All Payer Claims Data from 2006 to 2021, we included 119,422 pregnancies (Figure 1). The prevalence of HDP was 12.4% (Table 1). Preterm delivery, cesarean section, pre-existing diabetes, obesity, and pre-existing chronic hypertension were more commonly observed in the HDP group. The cumulative risk of cardiovascular disease within 24 months’ postpartum for those with HDP vs. without HDP was 0.6% vs. 0.2% for heart failure, 0.3% vs. 0.1% for ischemic heart disease, 0.2% vs. 0.2% for arrhythmia/cardiac arrest, 0.6% vs. 0.2% for cardiomyopathy, 0.8% vs. 0.4% for cerebrovascular disease/stroke; 1.6% vs. 0.7% for severe cardiac disease; and 9.7% vs. 1.5% for new chronic hypertension (Table 2).

Figure 1: Analytic Sample Identification.

^aPre-existing chronic hypertension was defined as hypertension from one year prior to conception to 20 weeks of gestation

Table 1:

Characteristics of deliveries in Maine 2007–2019

	Total	No hypertensive disorder of pregnancy		Hypertensive disorder of pregnancy
	N	N	Column %	N	Column %
Total	119422	104785	100.0	14637	100.0
Row %			87.6		12.4
Maternal age at delivery
Missing	50	42	0.0	a	a
15 to 19	7392	6548	6.3	844	5.8
20 to 24	28161	24903	23.8	3258	22.3
25 to 29	35761	31396	30.0	4365	29.8
30 to 34	30257	26487	25.3	3770	25.8
35+	17801	15409	14.7	2392	16.3
Stillbirth	626	563	0.5	63	0.4
Gestational age at delivery
At least 37 weeks	110450	97570	93.1	12880	88.0
20 to <37 weeks	8972	7215	6.9	1757	12.0
Cesarean Section	34452	28610	27.3	5842	39.9
Delivery number in dataset
1	79992	68943	65.8	11049	75.5
2 or more	39430	35842	34.2	3588	24.5
Insurance coverage
Medicaid	66014	58588	55.9	7426	50.7
Private	53120	45953	43.9	7167	49.0
Medicare	288	244	0.2	44	0.3
Pre-existing diabetes	3373	2490	2.4	883	6.0
Obesity	7165	5510	5.3	1655	11.3
Pre-pregnancy heart failure b	54	44	0.0	10	0.1
Pre-pregnancy heart disease b	58	46	0.0	12	0.1
Pre-pregnancy stroke b	191	158	0.2	33	0.2
Pre-pregnancy arrhythmia b	78	60	0.1	18	0.1
Pre-pregnancy cardiomyopathy b	77	60	0.1	17	0.1
Pre-existing chronic hypertensionb	8661	3323	3.2	5338	36.5

Data source: Maine Health Data Organization’s All Payer Claims Data

^aObservations were excluded from Cox regression modeling of the cardiovascular conditions being examined postpartum.

^bData counts between 1 and 9 suppressed from presentation.

Table 2:

Cumulative risk of diagnosis in the first 24 months’ postpartum for specific

	Total	Number of events postpartum	%a	HDP	Non-HDP	%b among exposed	%b among unexposed
Heart failure	119368	202	0.2	14627	104741	0.6	0.2
Ischemic heart disease	119364	121	0.2	14625	104739	0.3	0.1
Cerebrovascular disease/stroke	119231	443	0.5	14604	104627	0.8	0.4
Arrhythmia/cardiac arrest	119344	151	0.2	14619	104725	0.2	0.2
Cardiomyopathy	119345	213	0.2	14620	104725	0.6	0.2
Severe cardiac disease (heart failure, stroke, or cardiomyopathy)	119124	741	0.8	14582	104542	1.6	0.7
New chronic hypertension (43+ days after delivery) b	110761	1662	2.1	9299	101462	9.7	1.5

Data source: Maine Health Data Organization’s All Payer Claims Data

HDP=hypertensive disorder of pregnancy

^aCumulative risk by 24 months. Censoring events were loss of health insurance coverage or start of the next pregnancy, whichever was earlier. Each model excluded records with any diagnosis before pregnancy of the cardiovascular conditions being examined postpartum, and records with gestational age (<20 weeks), non-Maine residence, multifetal gestation, those with implausible time to next pregnancy (<60 days), and those without health insurance during pregnancy through the first 2 months’ postpartum.

^bHypertension diagnoses in the first 42 days’ postpartum were not included as chronic hypertension outcomes, as these were included in the definition of hypertensive disorders of pregnancy.

Unadjusted hazard ratios for diagnoses of CVD within the first 24 months’ postpartum for people with vs. without HDP were 4.40 (95% CI 3.32–5.84) for heart failure, 2.34 (95% CI 1.56–3.52) for ischemic heart disease, 2.06 (95% CI 1.64–2.58) for cerebrovascular disease/stroke, 1.21 (95% CI 0.77–1.91) for arrythmia/cardiac arrest, 4.13 (95% CI 3.11–5.48) for cardiomyopathy, and 2.69 (95% CI 2.28–3.16) for the composite outcome of severe cardiac disease. After adjusting for potential confounders, those with HDP had increased risks of heart failure (adjusted hazard ratio (aHR) 2.81 (95% CI 1.90–4.15)), cerebrovascular disease/stroke (aHR 1.43 (95% CI 1.07–1.91)), cardiomyopathy (2.90 (95% CI 1.96–4.27)), and severe cardiac disease (aHR 1.90 (95% CI 1.54–2.36)) within the first 24 months’ postpartum, as compared to those without HDP (Table 3, Figure 2). There was no association between HDP and ischemic heart disease ((aHR 0.92 (95% CI 0.55–1.54)) or cardiac arrest/arrhythmia ((aHR 0.90 (95% CI 0.52–1.51)). The unadjusted hazard ratio for new diagnoses of chronic hypertension within the first 24 months’ postpartum for people with vs. without HDP was 7.30 (95% CI 6.61–8.06); after adjusting for potential confounders, the hazard ratio changed little (aHR 7.29 (95% CI 6.57–8.09)).

Table 3:

Risk of CVD disease in first 24 months’ postpartum for women with hypertensive disorders of pregnancy (HDP), deliveries in Maine 2007–2019, n=119,422

	Unadjusted HR (95% CI)	Adjusted HR (95% CI) a
Heart failure
No-HDP	Reference	Reference
HDP	4.40 ( 3.32, 5.84)	2.81 ( 1.90, 4.15)
Ischemic heart disease
No-HDP	Reference	Reference
HDP	2.34 ( 1.56, 3.52)	0.92 ( 0.55, 1.54)
Cerebrovascular disease/stroke
No-HDP	Reference	Reference
HDP	2.06 ( 1.64, 2.58)	1.43 ( 1.07, 1.91)
Arrhythmia/cardiac arrest
No-HDP	Reference	Reference
HDP	1.21 ( 0.77, 1.91)	0.90 ( 0.52, 1.57)
Cardiomyopathy
No-HDP	Reference	Reference
HDP	4.13 ( 3.11, 5.48)	2.90 ( 1.96, 4.27)
Severe cardiac disease (heart failure, stroke, or cardiomyopathy)
No-HDP	Reference	Reference
HDP	2.69 (2.28, 3.16)	1.90 (1.54, 2.36)
New chronic hypertension (43+ days after delivery)b
No-HDP	Reference	Reference
HDP	7.30 ( 6.61, 8.06)	7.29 ( 6.57, 8.09)

Data source: Maine Health Data Organization’s All Payer Claims Data

CI=confidence interval; CVD= cardiovascular disease; HR= hazard ratio; HDP=hypertensive disorders of pregnancy

^aAdjusted for maternal age at time of delivery (continuous), pre-pregnancy depression (yes/no), pre-existing chronic hypertension (yes/no; for chronic hypertension models, these observations were excluded), pre-pregnancy diabetes (yes/no), obesity (yes/no), smoking (yes/no), nulliparity (yes/no), pregnancy number in dataset (continuous), year of delivery (continuous), Medicaid coverage during pregnancy (months covered, continuous), county-level measures (ratio of population to primary care physicians [continuous]; percentage uninsured adults [continuous]; percentage smoking adults [continuous]; percentage of adults with obesity [continuous]), ZIP-code level measures (percentage of non-white residents [continuous], percentage of adults with no Bachelor’s degree [continuous], percentage of persons living below poverty level [continuous]), prenatal depression (yes/no), and gestational diabetes (yes/no).

^bHypertension diagnoses in the first 42 days’ postpartum were not included as chronic hypertension outcomes, as these were included in the definition of hypertensive disorders of pregnancy.

Figure 2: Weighted adjusted.

^a cumulative hazard curves and 95% confidence interval bands for diagnosis of cardiovascular disease in the first 24 months’ postpartum among people with and without hypertensive disorders of pregnancy, deliveries in Maine 2007–2019, n= 119,422

^aAdjusted for maternal age at time of delivery, pre-pregnancy depression, pre-existing chronic hypertension (for chronic hypertension models, these observations were excluded), pre-pregnancy diabetes, obesity, smoking, nulliparity, pregnancy number in dataset, year of delivery, Medicaid coverage during pregnancy, county-level measures, ZIP-code level measures, prenatal depression, and gestational diabetes.

Month 0 = month of delivery

After rerunning the analyses stratified by pre-existing chronic hypertension, all of the previously established associations between HDP and CVD persisted for those without pre-existing chronic hypertension; however, no significant associations were found for those with pre-existing chronic hypertension (Supplemental Table 2)

Among people with HDP, the highest proportion of first cardiovascular disease diagnoses occurred during the first month postpartum for cardiomyopathy (44%), heart failure (39%), cerebrovascular disease/stroke (39%), and severe cardiac disease (41%) (Supplemental Figure 1). However, for ischemic heart disease, arrhythmia/cardiac arrest, and new chronic hypertension (after the first 42 days’ postpartum) the month of first diagnosis was distributed fairly uniformly across the first 24 months’ postpartum.

Comment

Principal Findings:

Postpartum patients with a HDP have a significantly increased risk of most but not all cardiovascular diseases within the first 24 months’ postpartum, even after adjusting for potential confounders. Specifically, those with a HDP have nearly three times the risk for heart failure and cardiomyopathy within 24 months’ postpartum than their normotensive counterparts. Overall, of the six CVD outcomes we examined, the strongest association was for HDP and chronic hypertension. Patients with HDP were over 7 times as likely to have new chronic hypertension within 24’ months postpartum compared to those without HDP. These associations between HDP and CVD persisted even in the population with no pre-existing chronic hypertension. Among women with HDP, the highest proportion of first diagnoses for cardiomyopathy (44%), heart failure (39%), cerebrovascular disease/stroke (39%), and severe cardiac disease (41%) occurred during the first month postpartum. There was no association between HDP and ischemic heart disease or arrhythmia/cardiac arrest.

Results in the Context of What is Known:

Our findings of the association of HDP with CVD within 24 months’ postpartum are in alignment with previously published literature on the risks of CVD up to 12 months’ postpartum. When examining the risk of new chronic hypertension, a prior prospective cohort found that those with HDP have significantly increased odds of new chronic hypertension within 6–12 months postpartum (aOR 4.60).⁶ Other studies also support our finding of a strong association of HDP with a composite marker of severe cardiac disease (chronic hypertension, cerebrovascular disease/stroke, or cardiomyopathy) from as soon as 1 year postpartum through up to 40 years after delivery.^{2,4–6,15,38–43} In addition, our results have biologic plausibility based on previous literature on the cardiovascular abnormalities that occur during pregnancies complicated by a HDP. The maternal heart undergoes profound remodeling, including progressive increase in left ventricular mass, which is often a predictor of cardiovascular risk in the non-pregnant patient.⁴⁴

Our findings of no associations between HDP and ischemic heart disease and HDP and arrythmia/cardiac arrest are somewhat unexpected. Prior studies found that individuals with preeclampsia have an increased risk of ischemic heart disease 11–27 years after delivery.^38,45,46 This discrepancy in findings can be explained by the physiology of ischemic heart disease, which is typically dependent on the development of atherosclerotic plaques and takes years to build to a clinically significant level.¹⁹ There are few studies that have examined the association between HDP and arrhythmia/cardiac arrest. Small retrospective studies report a modest association between HDP with arrhythmia, but they included follow-up of up to 40 years since delivery.⁴⁷ Our study is unique in that it examines these rare CVD outcomes within the immediate 24 months’ postpartum, which is a more clinically relevant time period because screenings and interventions could prevent downstream adverse cardiovascular events.

Clinical Implications:

Women’s cardiovascular health is a staggering public health problem because it leads to substantial premature and preventable morbidity and mortality. It is understudied, underdiagnosed, and undertreated.¹⁷ The first step in prioritizing women’s cardiovascular research and clinical care is to identify which specific cardiovascular diagnoses have the greatest risk profile postpartum for those with HDP ⁴⁸ This can inform individualized postpartum screening and intervention program that is timely and targeted to the most clinically relevant cardiovascular diseases.^14,49 The results of our study can inform this initiative because we found that HDP patients are at the highest risk for heart failure, stroke, cardiomyopathy, and new chronic hypertension in the first 24 months’ postpartum.

Therefore, while the well-known association between HDP and future CVD is indeed supported by our data, we present novel findings showing this association does not apply to all types of cardiovascular disease during the first 24 months’ postpartum. Future studies are needed to inform how to tailor postpartum cardiovascular screenings and interventions to specifically reduce the risk of these outcomes. Screenings could include a comprehensive history and physical exam, serum testing with cholesterol evaluation, diabetes evaluation, and possibly brain natriuretic peptide levels, cardiac imaging, and cardiology referral. In addition, since the highest proportion of first postpartum cardiovascular diagnoses for cardiomyopathy (44%), heart failure (39%), cerebrovascular disease/stroke (39%) occurred during month 0 postpartum (the month of delivery), patients with HDP may benefit from increased surveillance immediately postpartum and the use of a lower threshold for cardiac imaging and cardiology consultation. These screening and primary prevention interventions may preserve long-term cardiovascular health and improve maternal and neonatal outcomes in a subsequent pregnancy for patients with a HDP.

New chronic hypertension was distributed fairly uniformly across the first 24 months’ postpartum; this suggests that care specific to pregnancy complications should not be confined to the traditional 42-day postpartum period. Patients need access to care and resources that extend beyond 42 days’ postpartum. Our results provide evidence that supports advocacy efforts to extend insurance coverage and offer additional health resources for 24 months postpartum for those with pregnancy complications.⁵⁰ Likewise, providers must focus on improving the transition of care to primary care physicians and/or cardiologists after the immediate postpartum period.

Research Implications:

Our study presents novel findings that HDP is not universally associated with all CVD subtypes. While many prior studies used a composite CVD outcome to examine the association between placental syndromes (including HDP) and CVD, ^3,51 our findings suggest that HDP is not associated with ischemic heart disease or arrythmia/cardiac arrest in the initial 24 months’ postpartum. These CVD subtypes may not be appropriate to include in composite CVD measures. Future study in other more diverse populations are needed for confirmation.

As mentioned, few prior studies have examined the association of HDP with individual CVD diagnoses, highlighting the research implications of our study’s findings. While one prior study using birth certificate data found an 8-fold increased incidence of heart failure and 14-fold increased incidence of stroke for patients with preeclampsia, their outcomes included only a few major cardiovascular events and utilized composite outcomes that occurred during pregnancy through 36 months’ postpartum.⁵² Further research with more granularity into the types of cardiovascular diseases and their interplay with pregnancy is critical in order to clarify the causal pathway between HDP and CVD and inform evidence-based clinical recommendations.

Strengths and Limitations:

Our study had several strengths. It focuses on a highly clinically relevant question that can inform targeted screening and primary preventive strategies postpartum in order to mitigate premature cardiovascular morbidity and mortality for women. It is unique among the large growing body of literature on preeclampsia and cardiovascular disease in that it not only has a higher level of granularity in terms of cardiovascular disease but that it also focuses on the immediate 24 months after delivery. In addition, the Maine All Payer Claims Data is comprehensive because it includes public and private payer’s facility and professional claims from an entire state across 16 years, and allows for longer term follow-up beyond the traditional 42 days’ postpartum, regardless of change in insurance provider.

Limitations of our study include that it was limited to one state, so generalizability to other areas within the US may be limited. However, our prevalence of HDP is similar to national estimates.^49,53 While our database is comprehensive because it uses all payer claims and includes a longer duration of postpartum follow-up, it does not include race and ethnicity data. This is unfortunate, because it is well known that racial and ethnic disparities are a major component of cardiovascular morbidity and mortality among women.^48,54 We did not differentiate new CVD events that occurred only after delivery from ongoing CVD conditions that first occurred during pregnancy or the delivery hospitalization. In addition, we did not have an exclusion or washout period postpartum, which could have further allowed us to better identify truly new cardiovascular disease diagnoses. In addition, since we utilized claims data, there is a possibility of residual confounding due to inaccurate or missing diagnoses codes for medical conditions, e.g. obesity;⁵⁵ and we used population-level measures instead of individuallevel measures to define certain confounders (e.g. access to care), which are less accurate measures. While we used previously published algorithms to identify HDP based on ICD codes, these codes were not validated for our specific cohort against medical records.²⁶ Finally, although we did not see crossing curves in our visual assessment of Cox proportional hazards models (for our significant findings), there did appear to be some variation in the magnitude of hazard ratios over time, suggesting that modification of our Cox model may have useful.

Conclusions:

Patients with HDP have a substantially increased risk for heart failure, cerebrovascular disease/stroke, cardiomyopathy, and new chronic hypertension within 24 months’ postpartum. While prior literature has found an association between HDP and ischemic heart disease in the long term, our study does not show an association between HDP and ischemic heart disease in the first 24 months’ postpartum. Our results have the potential to inform lifesaving targeted postpartum intervention strategies that focus specifically on the cardiovascular risks that are increased postpartum. Further research to confirm these findings and development of multidisciplinary, individualized postpartum cardiovascular screening strategies are crucial to save our patients from premature, preventable morbidity and mortality.

Supplementary Material

4

Supplement Figure 1: Distribution of first diagnosis of cardiovascular disease within 24 months’ postpartum among people with and without hypertensive disorders of pregnancy, deliveries in Maine 2007–2019, n= 119,422

CONDENSATION:

Patients with hypertensive disorders of pregnancy have an increased risk for heart failure, cerebrovascular disease, cardiomyopathy, and new chronic hypertension in the first 24 months’ postpartum.

AJOG AT A GLANCE:

1. Why was this study conducted?

   • To identify the risk of significant cardiovascular diagnoses in the first 24 months’ postpartum among patients with hypertensive disorders of pregnancy
   • To determine when the highest incidences of cardiovascular disease diagnoses occur within 24 months’ postpartum
2. What are the key findings?

   • Those with hypertensive disorders of pregnancy have a significantly increased risk of postpartum diagnoses of heart failure, cerebrovascular disease, and cardiomyopathy. Most of the diagnoses occurred within the first month postpartum.
   • Those with hypertensive disorders of pregnancy have a significantly increased risk of new chronic hypertension within 24 months’ postpartum.
3. What does this study add to what is already known?

   • Since most existing data on hypertensive disorders of pregnancy and short-term cardiovascular disease risk is limited to the immediate postpartum period and focuses on overall CVD risk, we present novel findings on the association between hypertensive disorders of pregnancy and specific cardiovascular diseases during the first 24 months’ postpartum.