Breastfeeding and Postpartum Cardiovascular Health

Breastfeeding, Hypertension, Pregnancy-Induced, Hypertensive Disorder of Pregnancy, Pre-Eclampsia, Pregnancy Complications

Hypertensive disorders of pregnancy (HDP) are increasingly recognized sex-specific risk factors for premature cardiovascular disease (CVD) in women. HDP, including preeclampsia and gestational hypertension, confer a 2- to 3-fold increase in the risk of chronic hypertension and ischemic heart disease 10-15 years after delivery. Observational data suggest that breastfeeding can lower maternal blood pressure (BP), risk of metabolic syndrome, and other markers of cardiovascular risk in the short term and long term, possibly by helping to re-set the metabolic changes of pregnancy. The investigators recently demonstrated an 11% reduction in the risk of metabolic syndrome among postpartum women with a variety of complications in pregnancy, including HDP, who breastfed for \> 6 months, compared to those who did not breastfeed and those who breastfed for shorter durations. An analysis of 622 postpartum women at Kingston General Hospital showed that breastfeeding women had nearly a 6-mmHg lower systolic BP than women who did not breastfeed with an apparent dose-response effect of breastfeeding duration. Women with pregnancy complications including HDP are vulnerable to early weaning. Interactive, multi-modal approaches targeting a mother's breastfeeding self-efficacy (i.e., confidence about breastfeeding) have been effective in healthy postpartum women. However, these have not yet been tested specifically in HDP women, who stand to derive substantial benefit from breastfeeding. This is an important area to study since nurse-led breastfeeding supportive interventions can be widely applied to the postpartum care of women with HDP and can be integrated into comprehensive CVD risk reduction programs for these women. The primary outcome is postpartum BP, since hypertension is a key mediating factor in women's heart health. The investigators conducted a feasibility study of a breastfeeding self-efficacy intervention to enhance breastfeeding outcomes among women with HDP achieving pre-defined targets of a recruitment rate of \>50% , attrition rates of \< 30%, and \> 70% participant satisfaction with the intervention, measured at the 6-month time point. Additionally, data showed trends in both systolic and diastolic BP favoring the intervention group. The current study is a multi-site open-label randomized trial to assess for a difference in blood pressure and breastfeeding between groups, and to serve as a cohort of HDP women for longitudinal follow-up.

The present study aims to assess a nurse-led self-efficacy enhancing breastfeeding intervention in women who have HDP. The investigators will examine whether this intervention reduces postpartum blood pressure and improves breastfeeding outcomes in these women. In the long-term, the investigators will observe to see whether breastfeeding helps to lower the chance of chronic hypertension or other cardiovascular risk factors, as well as heart disease or stroke. Outcomes: As per study protocol amendment approved by the RI-MUHC Research Ethics Board on July 2023, all study aims (with the exception of the exploratory ones such as Objective 8, Biomarkers) now address an active 6-months follow up period, and a passive 12-months follow up allowing a shorter time for data analysis and study completion. This modification will align the end of study with the availability of funding resources. Previously, it was stated that All outcomes will be ascertained at the end of the study, which is at 12 months postpartum. The primary study endpoint is systolic and/or diastolic BP, in mmHg. Secondary study endpoints: * Breastfeeding outcomes: i. Duration of exclusive breastfeeding (weeks); ii. The proportion who breastfeed (exclusive or non-exclusive) at 6 months; * The presence of metabolic syndrome. Additional objectives: -to evaluate whether women who breastfeed for longer are more likely to engage in cardiovascular protective behaviors such as weight reduction, healthy eating and higher levels of physical activity at 12 months postpartum; to explore the biological and psychosocial determinants of breastfeeding behaviour within 12 months postpartum, measured at the time of delivery; to assess the risk of future hospitalization or emergency room visit for any cardiovascular event or procedure within 15 years after delivery, according to: (a) breastfeeding intervention, (b) total duration of breastfeeding, and (c) other novel determinants of cardiovascular risk; to collect biosamples among women who recently had HDP, in order to advance on the understanding of the different phenotypes of women and their associated cardio-metabolic risk in the short and long-term. Women who had HDP will be recruited from three participating centers. In Quebec there will be three (previously two) centers: (1) McGill University Health Centre-Royal Victoria Hospital (MUHC-RVH) and (2) St. Mary's Hospital Centre (SMHC) and the Jewish General Hospital (JGH), the fourth (previously third) site will be in Ontario at the (3) Kingston General Hospital (KGH). Participants that plan to breastfeed will be randomly divided into two groups: usual postpartum care + BSE intervention or usual postpartum care. Participants with HDP who are not planning to breastfeed will also be invited to participate as an additional observational comparison group. Study outcomes for all participants will be assessed by completion of questionnaires, home and in-office blood pressure measurement, basic metabolic biochemical testing and long-term follow-up via linkage with administrative health data. NOTE: The pandemic and other factors have led to delays in approvals at different sites, and associated challenges with recruitment. Due to these delays and funding deadlines, we revised sample size calculation with more realistic and less stringent assumptions. Sample size was modified from 323 to 221. This modification was approved by the RI-MUHC Research Ethics Board on July 2023

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