Interpretation
Hypertensive disorders of pregnancy are associated with increased CVD risk across multiple studies in diverse populations.(1,2) There is compelling evidence that hypertension accounts for much of the CVD risk following a hypertensive disorder of pregnancy, yet few interventions have been studied to reduce progression to hypertension after a hypertensive disorder of pregnancy.(27–29) Our previous work has demonstrated that overweight and obese individuals have high rates of ongoing hypertension at one-year postpartum and that overall individuals may be particularly motivated to lower blood pressure following a hypertensive disorder of pregnancy.(7)
Prior postpartum intervention studies have had high attrition rates, which suggested that postpartum individuals may not be willing to participate in intervention studies or engage in follow up care due to the competing demands of the immediate postpartum period.(17,18) We enrolled participants within the first six months postpartum and retained almost 90% to one-year. Our study design was adapted to meet institutional regulatory requirements in the setting of the COVID-19 pandemic, and a remote approach to recruitment and study visits may in fact be well suited to this population. Before transitioning to a remote approach, we offered individuals two options for the first study visit, in-office study visit or a home visit. Among these early participants, 58% (n=26) opted for a home study visit, highlighting the potential utility and desirability of this approach in the postpartum period as well as the synergy of community partnering. Our overall enrollment rates are in line with other studies of remote lifestyle interventions for weight loss postpartum, but future work is warranted to understand barriers to broaden enrollment of eligible participants. (30,31) Of the individuals who declined to participate, reasons cited included that being too busy or having the perception that their HDP “wasn’t that bad” so they didn’t need an intervention. Future work should focus on additional education and risk counseling in the postpartum period to enhance understanding of future CV risk following a HDP. Additionally, consideration of enhanced recruitment methods such as the use of social media platforms or using technology to identify and recruit participants and the use of community-based enrollment (e.g Women, Infants, Children [WIC] or doula community programs) or integration with a clinical postpartum visit may improve uptake of our intervention.
The parent Heart Health 4 Moms trial demonstrated improvement in knowledge of CVD risk and self-efficacy to achieve a healthy diet and decrease physical inactivity among predominantly white and highly educated individuals within the first five years following a pregnancy complicated by preeclampsia(8). The parent trial excluded individuals with BP ≥140/90 mmHg, who were on anti-hypertensive agents or had a BMI ≥40 kg/m2. Compared to the initial trial, by design, we enrolled a more diverse, higher-risk population, with 25% on anti-hypertensive agents and 25% with a BP ≥140/90 mmHg at enrollment. Importantly, we note that the majority of participants were able to come off anti-hypertensive agents during the trial period.
Recent work has demonstrated that pharmaceutical interventions in the immediate postpartum period may improve blood pressure and cardiovascular function in the first year postpartum.(32,33) The SNAP-HT trial randomized postpartum individuals who were on anti-hypertensive agents following a hypertensive disorder of pregnancy to usual care with in-office blood pressure assessments versus home blood pressure monitoring plus management with systematic titration of anti-hypertensive medications in the postpartum period. Cairns and colleagues found that this approach was feasible and resulted in improved diastolic blood pressure with a lowering of 4.5mmHg seen in the intervention group up to 6 months postpartum.(33) Similarly, individuals with preterm preeclampsia randomized to postpartum enalapril have improved diastolic function and left ventricular remodeling at 6 months postpartum when compared to individuals randomized to placebo.(32) These studies suggest that the immediate postpartum period may be particularly important for cardiovascular remodeling and that interventions in this period may improve both short and long-term cardiovascular risk.
Despite promising data in the non-pregnant population, few studies have investigated self-monitoring of BP combined with additional support. Our study found a modest lowering of blood pressure in the intervention arms. Given the evidence that modest BP elevations among young adults (<40 years) are linked to significantly higher risk for subsequent CV disease events when compared with those with normal BP, modest BP improvements may be important.(34) Although our findings are promising, the ongoing high rates of hypertension and need for anti-hypertensive medication suggest the potential need for interventions beyond home monitoring and lifestyle support in a proportion of this population. Thus, postpartum monitoring may help stratify groups for lifestyle versus more intensive follow-up to improve BP control. Our findings support the need for larger studies with longer follow up postpartum. One major limitation to interventions beyond the immediate postpartum period is access to care. For individuals with public health insurance, in many states within the United States, Medicaid coverage lasts only through sixty days postpartum. The high rates of ongoing hypertension in our population highlight the critical need for Medicaid expansion to at least one year postpartum and the importance of successful transitions of care postpartum from the obstetrician to the primary care physician.
We saw no improvement in self-efficacy towards healthy diet and activity or levels of physical activity and inactivity in the HH4NM + HBPM arm, perhaps related to the high levels of self-efficacy at baseline. We also saw no significant effect of our intervention on weight change. Prior studies have shown that diet alone and diet paired with exercise after delivery lead to greater weight loss compared to usual care in a general postpartum population, not specifically in overweight or obese individuals following a hypertensive disorder of pregnancy. A meta-analysis of 7 trials demonstrated that diet combined with exercise was significantly associated with postpartum weight loss with a mean difference of 1.93 kg.(35) The dietary counseling in our intervention was centered around implementing a DASH diet, as such, we note that total daily sodium consumption, as measured by the Block Sodium Screener decreased in the HH4NM + HBPM arm compared to the other two arms. Consistent with a non-pregnant and postpartum population, we found that higher sodium intake as assessed with the Sodium Screener was associated with higher blood pressure and that individuals with persistent hypertension at the conclusion of the study reported higher sodium intake.(36–38) These findings support the possibility of lower sodium intake leading to a greater reduction in blood pressure in the intervention arm of our study and warrant further investigation with more robust assessments such as urinary sodium excretion. This could be relevant, as a recent study in individuals approximately five years postpartum found that those with a history of preeclampsia have an impaired ability to adapt their arterial stiffness (as assessed by pulse wave velocity) in response to a change in sodium intake when compared to those with a history of normal pregnancy.(39)