Objective: Women with polycystic ovary syndrome (PCOS) have a worsened metabolic profile but the progression of cardiometabolic features over time is unclear. Understanding this natural history is a key priority in PCOS research and vital for guiding the prevention and management of this common condition. We explored cardiometabolic changes that are observed in women with PCOS compared to those without PCOS across the life course. Design, Patients and Measurements: A systematic review of longitudinal cohort studies was conducted across MEDLINE, EMBASE, Ovid PsycInfo, CINAHL PLUS and EBM reviews between 15 January 2020 and 11 February 2021. Eligible studies included participants with or without PCOS diagnosed according to the 2003 Rotterdam or the 1990 National Institutes of Health (NIH) criteria. We included studies that were published from the year 1990 to 2021 with data on cardiometabolic outcomes as per the PCOS core outcomes set. Results: There were 31 longitudinal studies with 28,316 participants from four continents. At the start of follow up, participants were aged between 1 year and 49 years with a follow-up period ranging from 2 to 32 years. Changes in BMI and the risk of coronary heart disease were similar in adult women with and without PCOS. Women with PCOS had a higher risk of Type 2 diabetes than their non-PCOS counterparts. Evidence for the majority of all other outcomes was conflicting and with inadequate data. Conclusion: Understanding the natural history of PCOS and particularly changes in cardiometabolic features remains challenging. Existing literature is extensive but heterogeneous and inconsistent. Longitudinal studies in unselected populations are needed to provide high-quality data in this area.