Introduction

Pregnancy has been described as a window to future health in women, particularly for future cardiovascular disease and death. This association is clearly seen in women who experience hypertensive disorders of pregnancy (HDP) and their risk of developing postpartum hypertension (HTN). HDP include gestational hypertension (GH), chronic hypertension, preeclampsia with and without severe features, and preeclampsia superimposed on chronic hypertension. HDP have been reported to complicate approximately 10–15% of pregnancies worldwide, and their prevalence is increasing [1]. Up to 350,000 women in the USA are diagnosed with preeclampsia every year [2], with the incidence increasing by 25% between 1987 and 2004 [3, 4]. HDP are associated with long-term cardiovascular morbidity and mortality, and these women are at a 2–4-fold increased risk of heart failure, acute coronary syndrome, and cerebrovascular events [5••] and a higher prevalence of postpartum HTN. These cardiovascular events are thought to be due to a direct impact on the cardiovascular system causing endothelial dysfunction in addition to their association with cardiovascular risk factors of obesity, physical inactivity, HTN, tobacco use, diabetes, and dyslipidemia. Approximately 16% of the USA’s maternal mortality has been attributed to HDP [6], and these women are at a 1.5-fold increased risk of death.

Postpartum HTN is vastly underrecognized. A recent study of 988 women admitted for cesarean section found 18.6% of women developed postpartum HTN; 41.8% of these cases were de novo HTN [7]. During the first year after delivery, women with HDP have a 12- to 25-fold greater risk of developing chronic HTN, which is the most common cause for hospital readmission. A large retrospective study found that 63% of patients readmitted with delayed postpartum preeclampsia had no antecedent diagnosis of a hypertensive disorder of pregnancy [8].

Criteria for the diagnosis of hypertension and hypertensive disorders of pregnancy

The American College of Cardiology/American Heart Association guidelines have reclassified blood pressure (BP) criteria for stages of HTN. Normal BP is defined as systolic BP <120 mmHg and diastolic BP <80 mmHg and elevated BP as systolic BP between 120 and 129 mmHg and diastolic BP <80 mmHg, followed by stage 1 and stage 2 HTN as shown in Table 1 [9]. HDP are classified as chronic HTN (diagnosed prior to pregnancy or before 20 weeks of gestation); gestational HTN (HTN with BP of ≥140/90 mmHg in the absence of proteinuria diagnosed at 20 weeks of gestation or later); preeclampsia/eclampsia (increase in BP to ≥140/90 with concomitant proteinuria or organ damage); and preeclampsia superimposed on chronic HTN [10] as shown in Table 2. It is important to note that obstetric societies have yet to adopt the 2017 AHA guidelines for HTN, and it is debated whether a change in the BP threshold to 130/80 mmHg for the diagnosis and treatment of chronic HTN would lead to a change in perinatal outcomes. There is a growing body of evidence that adoption of these lower limits for BP will identify women at higher risk of maternal and neonatal mortality and morbidity including development of preeclampsia, preterm birth, and small for gestational age infants [11,12,13].

Table 1 ACC/AHA stages and definition of hypertension
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Table 2 ACOG definitions of hypertensive disorders of pregnancy
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Risk factors for the development of postpartum hypertension

Despite the risk of immediate and future cardiac events associated with HDP, there are limited data regarding the risk factors that predispose certain women to this complication. There appears to be a dose-dependent effect of HDP and the risk of developing chronic HTN later in life in that the more severe the HTN was during pregnancy, the greater the risk. Chronic HTN is more likely to occur when GH occurs earlier in pregnancy and when the pregnancy is associated with iatrogenic preterm delivery and fetal growth disorders. In a study by Hauspurg et al. evaluating BP in nulliparous women, BP category and trajectory early in the pregnancy were independently associated with the risk of preeclampsia and GH [14]. The recurrence of preeclampsia in subsequent pregnancies has been shown to increase the risk of the development of chronic HTN when compared to women without recurrence [15]. Tooher et al. performed a retrospective analysis of 31,656 women, finding that 13.8% had HDP and 34% of this cohort had severe HTN defined as BP ≥170/110 mmHg [5••]. The women with severe HTN tended to be older, delivered earlier, and had lower neonatal weights when compared to women who were normotensive during pregnancy. Goel et al. have shown that women with a higher body mass index and pregestational diabetes mellitus were more likely to develop postpartum HTN [7]. Finally, there are racial disparities with regard to the development of postpartum HTN. In a prospective study by Hauspurg et al. of 1077 women with HDP, BP rapidly decreased after 3 weeks and then stabilized in the majority of the population. However, black women had less of a rapid decline in BP compared to white women. At the end of the program, 68.1% of black women, compared to 51.4% of white women, met criteria for stage 1 or 2 HTN [16].

Etiologies and evaluation of postpartum hypertension

Postpartum HTN can be due to persistent GH, preeclampsia, or preexisting HTN. However, it may also be due to new-onset essential or de novo postpartum HTN or due to a secondary cause of HTN. HELLP syndrome (hemolysis, elevated liver function tests, and low platelet count) occurs in 30% of women during the postpartum period and is often considered to be on the spectrum of preeclampsia-related disorders. Other causes include pain medications such as nonsteroidal anti-inflammatory medications which can cause vasoconstriction and subsequent retention of sodium and water and HTN. Ergot alkaloids, like methylergonovine, are used at times for uterine atony and can also cause vasoconstriction and HTN. BP can also be elevated in patients with peripartum cardiomyopathy manifested by signs and symptoms of fluid retention as noted in Table 3. HTN associated with thunderclap headaches, focal neurological deficits, visual changes, and seizures should be suspected as having neurological causes or sequelae of HTN such as cerebrovascular accident or reversible vasoconstriction syndrome. Reversible vasoconstriction syndrome compromises a group of conditions that cause multifocal narrowing of the cerebral arteries and neurological symptoms. It is more common in women, is associated with pregnancy, and is thought to be related to changes in estrogen and progesterone levels. These patients should be immediately evaluated by neurology and undergo computed tomography and magnetic resonance imaging of the brain and possible cerebral venography. Less than 20% of patients will have residual neurological symptoms, and these deficits are usually considered minor in severity. Finally, endocrine disorders as well as primary renal disorders are other etiologies of postpartum HTN; a comprehensive list as well as their common signs and symptoms are listed in Table 3.

Table 3 Etiology of postpartum hypertension
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The evaluation and management of postpartum HTN will depend on the history including cardiac risk factors, active medications including the use of antihypertensive therapy during pregnancy, BP measurements during pregnancy, physical exam with particular attention to signs and symptoms of fluid overload, and the results of initial laboratory and imaging tests [17]. BP in patients with preeclampsia will usually decrease within 48 h after delivery but will often increase again after 3–6 days due to postpartum volume shifts.

Complications of postpartum hypertension

In the immediate postpartum period, women with HDP are at a higher risk of hypertensive urgency/emergency and stroke. The most common cause of death in women with preeclampsia is intracerebral hemorrhage. Women who develop postpartum hypertension after completing a pregnancy with normal blood pressures are at a higher risk of seizures due to postpartum eclampsia which is associated with significant morbidity and mortality.

Women with preeclampsia are at a high risk of progression to chronic HTN or persistent HTN during the first year following HDP. A study evaluating ambulatory BP monitoring (measuring BP over a continuous 24-h period) and office BP readings of women with preeclampsia with severe features demonstrated that 42% had persistent HTN at 1 year with approximately 18% discovered by ambulatory monitoring [18]. This study highlights how informative frequent office visits and ambulatory BP measurement can be in the surveillance and management of postpartum hypertension in patients with elevated risk.

Treatment

The data regarding effective pharmacological treatment of postpartum HTN are limited. Beta-blockers and calcium channel blockers are most commonly used and have been shown to enter breast milk but at a level that appears to be safe for the infant [19]. In a meta-analysis of 39 studies by Cairns et al., the authors were not able to recommend one specific antihypertensive medication or BP threshold for the management of postpartum HTN because the results of each study were so variable [20]. This highlights the significant gap in knowledge on how to treat this patient population, which medications are more effective, and the thresholds for initiation, escalation, and discontinuation. Medications that are considered safe to use in the postpartum period while breast feeding are listed in Table 4 with their mechanisms of action and common side effects. Some commonly used postpartum antihypertensive medications include labetalol, diltiazem, nifedipine, hydrochlorothiazide, and captopril. In a randomized control of 90 postpartum women with HDP (defined as a systolic blood pressure ≥ 180 mmHg and/or diastolic blood pressure ≥ 110 mmHg requiring magnesium sulfate) who were randomized equally to treatment with clonidine vs. captopril, the primary outcome was elevated BP episodes in the intensive care unit. There was a trend toward fewer hypertensive episodes, greater systolic BP reduction, and fewer women requiring intravenous sodium nitroprusside in the group receiving clonidine; however, this was not statistically significant. Adverse reactions were more common but not significantly different in the captopril group (28.8%) vs. the clonidine group (18.6%) with the most common being dry cough, nausea, rash, and fever [23]. Patients with preeclampsia with severe features, eclampsia, or HELLP syndrome are usually treated with intravenous magnesium sulfate and antihypertensive medications with most improving within 48 h of onset [17].

Table 4 Medications for management of hypertension during lactation
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The use of furosemide in conjunction with other oral antihypertensive medications has also shown promise in controlling postpartum BP and reducing the number of agents needed for BP control. Ascarelli et al. performed a randomized controlled trial comparing furosemide to no therapy and noted that patients with preeclampsia with severe features who received furosemide had lower systolic BP by postpartum day 2 and required less antihypertensive therapy during hospitalization [24]. Perdigao et al. also performed a randomized, double-blind, placebo-controlled trial of a 5-day course of oral furosemide in women with both gestational HTN and preeclampsia with and without severe features, and they noted a 60% reduction in the prevalence of persistently elevated BP at 7 days [25].

Diet and exercise

There is little data examining the role of diet and exercise intervention during and after pregnancy. A Cochrane systemic review of randomized control trials evaluated 49 trials with such interventions and included 11,444 women [26]. Overall, weight management interventions led to a reduction in the number of women gaining excess weight by approximately 20% over the duration of their pregnancy. The authors found no clear benefit of diet or exercise interventions, or both, on the incidence of preeclampsia, cesarean section, and preterm birth. However, maternal HTN was reduced with these interventions. The benefits of the DASH diet (Dietary Approaches to Stop Hypertension) trial of consuming more fruits, vegetables, and low-fat dairy products in patients with systolic BP <160 mmHg and diastolic BP of 80-95 mmHg were shown to have a reduction in systolic and diastolic BP by 5.5 and 3 mmHg, respectively [27]. In a recent meta-analysis of 41 trials, the DASH diet and a lacto-ovo vegetarian diet reduced systolic BP by 5.5 mmHg on average, which was a larger reduction than the effects of a Mediterranean diet, high-fiber diet, and vegan diet [28]. These studies did not include pregnant women, however, highlighting the need for investigations evaluating the impact of diet and exercise on BP during and after pregnancy.

Monitoring

The National Institute for Health and Care Excellence recommends frequent BP monitoring during the postnatal period in patients with preeclampsia and GH. They recommend BP checks every 1–2 days for 2 weeks in the former and once in days 3–4 for the latter. The American College of Obstetricians and Gynecologists (ACOG) Guidelines suggest BP monitoring in the first 72 h postpartum and 7 to 10 days after delivery for women with HDP, although the supporting evidence is limited [29••]. Asymptomatic women can be discharged with ambulatory monitoring and discontinuation of antihypertensive medications if BP readings remain normal according to ACOG criteria. Women with mild HTN may be discharged prior to 72 h with close follow-up.

Recently, it has been recommended to screen women who experience complications during pregnancy for cardiovascular risk factors during the postpartum period, and it is urged to establish best practices at a local level to implement such screening [30]. Traditionally, the postpartum visit occurs 6 weeks after delivery; however, it has been shown that close to half of women do not attend this visit. Women with HDP have been shown to attend these visits more often than normotensive women; however, the overall attendance rates remain low. In a retrospective cohort study by Lewey at al., using insurance claims from a US health insurance database of 566,059 women who completed pregnancies between 2005 and 2014, 11% had HDP and 4% had chronic HTN. Only 58% of women with HDP had a 6-month follow-up with any continuity provider and 26% at 1 year. Risk factors associated with a lower rate of follow-up included age ≥ 30, Black race, Hispanic ethnicity, and a history of multiparity. These low rates of follow-up are missed opportunities for cardiovascular screening and cardiac risk management in these women.

In an attempt to address this, the ACOG created a postpartum evaluation algorithm which assigns responsibility to the maternal primary care provider for comprehensive postpartum care. They recommend a BP check 3–10 days after delivery and that high-risk patients be scheduled for follow-up within 1–3 weeks [29••]. ACOG recommends contact with all women within the first 3 weeks, ongoing follow-up from 3 to 12 weeks postpartum, and a comprehensive postpartum visit with transition to well-woman care at 4–12 weeks. Figure 1 provides a timeline for recommended postpartum BP checks and clinic visits for women with HDP.

Fig. 1
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Timeline of follow-up after delivery for patients who had a hypertensive disorder in pregnancy

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To further emphasize the importance of postpartum care, the ACOG has coined the term the “4th trimester” to address the physical, mental, and emotional challenges that women face during the 3 months after delivery. Providers should aim to have a postpartum visit occurring 3 weeks postpartum which would provide an early opportunity to screen for cardiovascular risk factors such as hypertension, dyslipidemia, physical inactivity, obesity, impaired glucose tolerance, and diabetes. The medical providers involved in this postpartum visit can include those from internal medicine, family medicine, and obstetrics and gynecology. Also, since the requirements for antihypertensive therapy change during the postpartum period with many patients requiring higher doses immediately postpartum and a majority of patients being treatment-free by 3–6 months [20], frequent monitoring will allow these changes to be made in a timely, supervised fashion.

Prevention

Approximately 77% of the excess long-term cardiovascular risk associated with HDP is due to modifiable risk factors [31]. Medical providers caring for postpartum women should be educated about the importance of monitoring BP early after delivery and should also include assessment of other cardiac risk factors. Groenhof et al. estimated that 9 women around the age of 35 years would need to be screened to detect 1 clinically relevant case of HTN, highlighting the small number of women that need to be screened to make a significant impact.

In order to consistently screen women for postpartum HTN, there is a need for a structured, comprehensive, and systematic approach. Creating comprehensive guidelines and implementing best practices at a local level regarding the frequency and monitoring are also a crucial part for helping healthcare professionals care for these women. Evidence based recommendations regarding the categories of antihypertensive medications that are most effective as well as guidance for the escalation and de-escalation of these medications would be important to improve postpartum care.

The importance of providing education to pregnant women with HDP is critical. Discharge instructions should emphasize the importance of BP monitoring, how to check their BPs, and education about the signs and symptoms of severe HTN. Ideally, these patients should be provided a blood pressure monitoring device prior to discharge. Most women with HDP are not aware of the association of HDP with future cardiovascular events, and it is important that they understand that risk. This will empower them to engage in their care and modify their risk factors with self-tracking and monitoring. Ambulatory blood pressure monitoring is easy to use and inexpensive and allows for monitoring of blood pressure over an extended period of time [32].

While some of this crucial patient education can be done during a 6-week postpartum visit, the overall poor attendance of patients at this visit significantly hinders a provider’s ability to do so. There are numerous barriers to attending these postpartum visits that need to be recognized and addressed. Women face postpartum fatigue, pain, postpartum depression and exacerbation of mental illness, infant caretaking and feeding, as well as childcare for other dependents during the timeframe of these visits. Finally, many women lose their healthcare coverage 6 weeks after delivery. Digital health and tele-visits would improve access for these women and address some of the barriers mentioned above.

Finally, there is an economic incentive to screen these women as there is a significant healthcare cost for the treatment of patients with preeclampsia. One study estimated a cost of $2.18 billion for these patients and their infants for 12 months post-delivery in 2012 [6].

Mobile health interventions in postpartum hypertension management

Early postpartum healthcare follow-up has been associated with better maternal and fetal outcomes [33]. Yet unfortunately, it has been estimated that only 40% of women attend face-to-face follow-up with a healthcare provider 6 weeks after delivery [29••]. This emphasizes the need for innovative models to improve rates of follow-up and better accessibility of healthcare monitoring and intervention for postpartum women.

Digital health resources and interventions are becoming readily available and more popular among mothers when compared to in-person follow-up. This is likely due to lower burden of transportation, less cost, and availability of online support. In the Framingham Health eHeart study, women were shown to have higher enrollment rates than men in digital blood pressure and activity tracking with a Fitbit over the course of a 5-month intervention [34].

In a case control study by Van den Heuvel et al., a care plan was designed with reduced visits enhanced with a digital platform for daily blood pressure and symptom monitoring starting from 16 weeks of gestation and compared to a retrospective control group managed without self-monitoring. Women enrolled in the digital platform had lower antenatal visits, yet fewer admissions for hypertension or suspected preeclampsia [35••]. A prospective single-cohort feasibility study was done at the University of Wisconsin to investigate the feasibility of telehealth with remote blood pressure monitoring for management of hypertension in postpartum women at risk of severe hypertension after hospital discharge. Participants received a tablet and equipment to transmit vital signs to a central monitoring site daily and participated in telehealth or telephone visits with a nurse at 48 h and as needed. Among study participants, the incidence of severe HTN after discharge was 16%; 53% of participants required treatment due to exacerbations in BP after discharge. There were no hospital readmissions, and, overall, 86% of participants were satisfied with the remote monitoring. Text message–based programs have been shown to improve patient engagement and BP monitoring [36]. Telehealth is a promising platform for postpartum HTN management to improve maternal morbidity and decrease hospital readmissions.

Conclusion

In general, there are three times during a woman’s life that she routinely receives medical care: infancy, pregnancy/postpartum, and when she develops a chronic medical condition. The postpartum period provides an opportunity for medical providers to screen for cardiovascular risk factors and conditions. HDP are a common complication of pregnancy and often underdiagnosed and treated in the postpartum period despite a well-established association with significant maternal cardiovascular morbidity and mortality. Prevention and detection are key. Optimization of women’s health status not only improves their outcomes during future pregnancies but also decreases cardiovascular events and mortality in the long term.