Breastfeeding and Postpartum Cardiovascular Health

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